Fig 1 - uploaded by Matthias Frank
Content may be subject to copyright.
Source publication
This chapter describes the perceptual properties of auditory events, the sound images that we localize in terms of direction and width, when distributing a signal with different amplitudes to one or a couple of loudspeakers. These amplitude differences are what methods for amplitude panning implement, and they are also what mapping of any coinciden...
Contexts in source publication
Context 1
... on the angle ϕ of the sound source. Equation (1.2) maps a single sound s from ϕ to the mid W and side Y signals by the gains [W, Y ] Decoding of MS signals to a stereo loudspeaker pair. Decoding of the mid-side signal pair to left and right loudspeaker is done by feeding both signals to both loudspeakers, however out-of-phase for the side signal, Fig. ...
Context 2
... width. Modifying the mid versus side signal balance before stereo playback, using a blending parameter α, allows to change the width of the stereo image from α = 0 (narrow) to α = 1 (full), Fig. 1.4a, see also ...
Context 3
... record the Ambisonic channels W, X, Y, one can use a Double-MS arrangement as shown in Fig. ...
Context 4
... -angled cardioids. Extending the MS scheme for recording with cardioid microphones, Fig. 1.3, cardioid microphones could be used to obtain the front-back and left-right figure-of-eight pickup patterns by corresponding pair-wise differences, and one omnidirectional pattern as their sum, Fig. 1.6. However, the use of 4 microphones for only 3 output signals is inefficient. Combining all the three microphone signals yields an ...
Context 5
... -angled cardioids. Extending the MS scheme for recording with cardioid microphones, Fig. 1.3, cardioid microphones could be used to obtain the front-back and left-right figure-of-eight pickup patterns by corresponding pair-wise differences, and one omnidirectional pattern as their sum, Fig. 1.6. However, the use of 4 microphones for only 3 output signals is inefficient. Combining all the three microphone signals yields an omnidirectional pickup pattern as N −1 k=0 cos(ϕ + 2π N k) = 0. Moreover introducing the differences between the front and two back microphone signals and between the left and right microphone signals yields ...
Context 6
... effect is important for head-tracked headphone playback to render the VR/360 • audio scene static around the listener. A complete playback system is shown in Fig. 1.9. The big advantage of such a system is that rotational updates can be done at high control rates and the HRIRs of the convolver are ...
Context 7
... pickup pattern aiming at θ 1 is described by , to produce the direction dipoles θ T X θ, 3D Ambisonic recording with a tetrahedral arrangement of cardioids. The principle that worked for three cardioid microphones on the horizon also works for a coincident tetrahedron microphone array of cardioids with the aiming directions FLU-FRD-BLD-BRU, see Fig. 1.11, and [12], Encoding is achieved there by the matrix that adds all microphone signals in the first line (W omnidirectional), subtracts back from front microphone signals in the second line (X figure-of-eight), subtracts right from left microphone signals in the third line (Y figure-of-eight), and subtracts down from up microphone ...
Context 8
... the matrix that adds all microphone signals in the first line (W omnidirectional), subtracts back from front microphone signals in the second line (X figure-of-eight), subtracts right from left microphone signals in the third line (Y figure-of-eight), and subtracts down from up microphone signals in the last line (Z figure-of-eight), see also As Fig. 1.12 shows, practical microphone layouts should be as closely spaced as possible. Nevertheless for high frequencies, the microphones cannot be considered coincident anymore, and besides a directional error, there will be a loss of presence in the diffuse field. Typically a shelving filter is used to slightly boost high ...
Context 9
... iemlib (free download within pure-data) Figure 1.13 gives an example for horizontal (2D) first-order Ambisonic panning, decoded to 4 loudspeaker and 2 headphone signals. ...
Context 10
... iemlib (free download within pure-data) Figure 1.13 gives an example for horizontal (2D) first-order Ambisonic panning, decoded to 4 loudspeaker and 2 headphone signals. Figure 1.14 shows the processing inside the Pd abstraction [FOA_binaural_decoder] contained in the Fig. 1.13 example, which uses SADIE database 1 subject 1 (KU100 dummy head) HRIRs to render headphone signals. ...
Context 11
... iemlib (free download within pure-data) Figure 1.13 gives an example for horizontal (2D) first-order Ambisonic panning, decoded to 4 loudspeaker and 2 headphone signals. Figure 1.14 shows the processing inside the Pd abstraction [FOA_binaural_decoder] contained in the Fig. 1.13 example, which uses SADIE database 1 subject 1 (KU100 dummy head) HRIRs to render headphone signals. Figure 1.15 sketches a first-order Ambisonic panning in 3D with decoding to an octahedral loudspeaker layout; master level [multiline∼] and hardware outlets [dac∼] were omitted for easier ...
Context 12
... 1.14 shows the processing inside the Pd abstraction [FOA_binaural_decoder] contained in the Fig. 1.13 example, which uses SADIE database 1 subject 1 (KU100 dummy head) HRIRs to render headphone signals. Figure 1.15 sketches a first-order Ambisonic panning in 3D with decoding to an octahedral loudspeaker layout; master level [multiline∼] and hardware outlets [dac∼] were omitted for easier readability. ...
Context 13
... source and importing a mono/stereo audio file (per drag-and-drop), the next step is the setup of the track channels. As shown in the table, the virtual source has a single-channel (mono) input and 4 output channels to send the 4 channels of first-order Ambisonics to the Master. The option to send to the Master is activated by default, cf. left in Fig. 1.16. The Master track itself requires 4 input channels and 6 output channels to feed the 6 loudspeakers (right). In Reaper, there is no separate adjustment for input and output channels, thus the Master track has to be set to 6 ...
Context 14
... the source track FX, the ambix_encoder_o1 can be used to encode the virtual source signal at an arbitrary location on a sphere by inserting the plug-in into the track of the virtual source, cf. its panning GUI in Fig. 1.17. For adding more sources, the track of the virtual source can simply be copied or duplicated. All effects and routing options are maintained for the new ...
Context 15
... the decoding matrix and its channel sequence and normalization. For the exemplary octahedral setup with 6 loudspeakers, the following text can be copied to a text file and saved as config-file, e.g., "octahedral.config". The decoder After loading the preset into the decoder plug-in, the decoder can generate the loudspeaker signals as shown in Fig. 1.18. In the example, the virtual source is panned to the front, resulting in the highest level for loudspeaker 1 (front). The loudspeaker 3 (back) is 12dB quieter because of a side-lobe suppressing super cardioid weighting implied by the switch /coeff_scale n3d, as a trick to keep things ...
Context 16
... shown on the SADIE-II website, 2 the SADIE-II head-related impulse responses can be used to rendering Ambisonics to headphones. The listing below shows a configuration file to be used with ambix_binaural, cf. Fig. 1.19, again using the trick to select n3d to keep the numbers simple and super-cardioid weighting #GLOBAL /coeff_scale n3d /coeff_seq acn #END #HRTF 44K_16bit/azi_0,0_ele_0,0.wav 44K_16bit/azi_90,0_ele_0,0.wav 44K_16bit/azi_180,0_ele_0,0.wav 44K_16bit/azi_270,0_ele_0,0.wav 44K_16bit/azi_0,0_ele_90,0.wav 44K_16bit/azi_0,0_ele_-90,0.wav ...
Context 17
... that delay-based stereophonic recording, such as AB, or equivalence-based recording, such as ORTF, INA5, etc., is often required and wellknown in its mapping properties for spaciousness and diffuseness, correspondingly. What is nice about higher-order Ambisonics: it can make use of these benefits by embedding such recordings appropriately, see Fig. ...
Context 18
... about higher orders: Ambisonics extended to higher orders permits a refinement of the directional resolution and hereby improves the mapping of uncorrelated sounds in playback. Figure 1.21a shows the correlation introduced in two neighboring loudspeaker signals when using Ambisonics, given their spacing of 60 • . ...
Context 19
... sounds in playback. Figure 1.21a shows the correlation introduced in two neighboring loudspeaker signals when using Ambisonics, given their spacing of 60 • . Given the just noticeable difference (JND) of the inter-aural cross correlation, the figure indicates that an Ambisonic order of ≥3 might be necessary to perceptually preserve decorrelation. Fig. 1.20 How is a microphone tree represented in Ambisonics, when it consist of 6 cardioids spaced by 60 cm and 60 • on a horizontal ring, and a ring of 4 super cardioids spaced by 40 cm and 90 • as height layer, pointing upwards? (b) Perceived depth in dependence of Ambisonics playback order for two listening positions (a) Inter-channel cross ...
Context 20
... this reason, the perception of spatial depth strongly improves when increasing the Ambisonic order from 1 up to 3, Fig. 1.21b. However, this is only the case when seated at the central listening position. Outside this sweet spot, higher orders than 3, e.g., 5, additionally improve the mapping of depth [19]. Therefore, higher-order Ambisonics is important for preserving spatial impressions and when supplying a large audience. Figure 1.22 shows that the ...
Context 21
... higher-order Ambisonics is important for preserving spatial impressions and when supplying a large audience. Figure 1.22 shows that the sweet area of perceptually plausible playback increases with the Ambisonic order [20]. With fifth-order Ambisonics, nearly all the area spanned by the horizontal loudspeakers at the IEM CUBE, the 12 × 10 m concert space at our lab, becomes a valid listening area. ...
Context 22
... Frank [10] investigated the auditory source width for frontal loudspeaker pairs with 0 dB level difference and various aperture angles, as well as the influence of an additional center loudspeaker on the auditory source width. The response was given by reading numbers off a left-right symmetric scale written on the loudspeaker arrangement ( Fig. 2.11). Figure 2.11 (right) shows the statistical analysis of the responses. Obviously the additional center loudspeaker decreases the auditory source ...
Context 23
... 2 Auditory Events of Multi-loudspeaker Playback Fig. 2.13 Model of the perceived width as 5 8 of the half-angle arccos r E matches the half-angle of the experiment. Except for a lower limit, which is determined by the apparent source width (ASW) due to the room acoustical setting For an additional center loudspeaker g 3 = 1, θ T = (1, 0), the estimator ...
Context 24
... compared to C, R. In order to avoid a strong increase in source width or annoying phasing effects, the outmost loudspeakers L and R are strongly reduced in their level, typically around -12dB compared to loudspeaker C. In doing so, the similarity of the comb filters yields barely any coloration when moving a source between the two directions, cf. Fig. ...
Context 25
... Correspondingly, the perceived directions shown in the gray 5 • -histogram bubbles of Fig. 3.7 indicate the perceived directions when the listener is located left-shifted off-center. While localization is slightly attracted by the closer loudspeaker at 0 • , the larger spread causes a more monotonic outcome that is less split than with VBAP in Fig. ...
Context 26
... well would diffuse signals be preserved played back? All the above experiments deal with how non-diffuse signals are presented. To complement what is shown in Fig. 1.21 of Chap. 1 with an explanation, the relation between Ambisonic order and its ability to preserve diffuse fields is estimated here by the covariance between uncorrelated directions. Assume a max-r E -weighted Nth-order Ambisonic panning function g(θ T s θ ) that is normalized to g(1) = 1, encodes two sounds s 1,2 from two directions ...
Context 27
... result was presented in Fig. 1.21 and was used to argue that the directional separation of first-order Ambisonics by its high crosstalk term g 12 might be too weak. Higher-order Ambisonics decreases this directional crosstalk and therefore improves the representation of diffuse sound ...
Context 28
... pre-calculated. Note the similarity to the first-order 2D example of Fig. 1.13, to which the main change is the use of the circular harmonics matrix ...
Context 29
... decoding to headphones, programming in Pd also looks rather similar as in the first-order example in Fig. 1 loudspeaker positions need to be employed. To work in 3 dimensions, programming in Pd would also be similar as in the corresponding first-order example of Fig. 1.15, using the matrix object [mtx_spherical_harmonics]. Typically, pre-calculated decoders including AllRAD and max-r E are used and loaded by, e.g., [mtx D.mtx] into Pd to ...
Context 30
... decoding to headphones, programming in Pd also looks rather similar as in the first-order example in Fig. 1 loudspeaker positions need to be employed. To work in 3 dimensions, programming in Pd would also be similar as in the corresponding first-order example of Fig. 1.15, using the matrix object [mtx_spherical_harmonics]. Typically, pre-calculated decoders including AllRAD and max-r E are used and loaded by, e.g., [mtx D.mtx] into Pd to keep programming ...
Context 31
... typical audio processing steps for Ambisonic surround-sound signal manipulation are shown in the block diagram Fig. 5.1 from [2]. The description of the multi-venue application in [3] and one for live effects [4] might be ...
Context 32
... are two ways of employing parametric equalizers to Ambisonic channels. Either a single-/multi-channel input of a mono-encoder or a multiple-input encoder is filtered by parametric equalizers. Or each of the Ambisonic signal's channels is filtered by the same parametric equalizer, see Fig. 5.11a. Fig. 5.11 Block diagram of processing that commonly and equally affects all Ambisonic signals, such as parametric equalization and dynamic processing (compression), without recombining the signals Bass management is often important to not overdrive smaller loudspeaker systems of, e.g., a 5th-order hemispherical playback system with ...
Context 33
... are two ways of employing parametric equalizers to Ambisonic channels. Either a single-/multi-channel input of a mono-encoder or a multiple-input encoder is filtered by parametric equalizers. Or each of the Ambisonic signal's channels is filtered by the same parametric equalizer, see Fig. 5.11a. Fig. 5.11 Block diagram of processing that commonly and equally affects all Ambisonic signals, such as parametric equalization and dynamic processing (compression), without recombining the signals Bass management is often important to not overdrive smaller loudspeaker systems of, e.g., a 5th-order hemispherical playback system with subwoofer ...
Context 34
... signal was speech and as a reference it used the frontal loudspeaker with the unprocessed signal "REF". The experiment tested the algorithm with both the symmetric impulse responses suggested by Eq. (5.18), and such truncated to their causal q ≥ 0-side, for a listening position at the center of the arrangement (bullet marker) and at 1.25 m shifted to the right, off-center (square marker). Figure 5.12 indicates for the widening algorithm with τ = 1.5 ms that the perceived width saturates above N > 2 at both listening positions. ...
Context 35
... to their causal q ≥ 0-side, for a listening position at the center of the arrangement (bullet marker) and at 1.25 m shifted to the right, off-center (square marker). Figure 5.12 indicates for the widening algorithm with τ = 1.5 ms that the perceived width saturates above N > 2 at both listening positions. Despite the effect of the causal-sided Fig. 5.12 Perceived width (left) and audio quality (right) of frequency-dependent dispersive Ambisonic rotation as widening effect using the setting τ = 1.5 ms, the Ambisonic orders N = 1, 2, 3, 5, and L = 3, 4, 5, 7 loudspeakers on the frontal semi-circle, with listening positions at the center (bullet marker) and half-way right off-center ...
Context 36
... Perceived width (left) and audio quality (right) of frequency-dependent dispersive Ambisonic rotation as widening effect using the setting τ = 1.5 ms, the Ambisonic orders N = 1, 2, 3, 5, and L = 3, 4, 5, 7 loudspeakers on the frontal semi-circle, with listening positions at the center (bullet marker) and half-way right off-center (square marker) Fig. 5.13 Perceived width (left) and audio quality (right) of frequency-dependent dispersive Ambisonic rotation as distance/diffuseness effect using the setting τ = 15 ms, the Ambisonic orders N = 1, 2, 3, 5, and L = 3, 4, 5, 7 loudspeakers on the frontal semi-circle, with listening positions at the center (bullet marker) and half-way right ...
Context 37
... more pronounced preference of the causal-sided implementation in terms of audio quality is found in Fig. 5.13 for the setting τ = 15 ms, where the algorithm is increasing the diffuseness or perceived distance for orders N > 2 at both listening ...
Context 38
... nearest loudspeakers. One can observe that rendering diffuse reverberation for a large audience benefits from a high Ambisonic order. Moreover, experiments in [43] revealed an improvement of the perceived spatial depth mapping, i.e. a clearer separation between foreground and background sound for the SDM-processed higher-order reverberation, cf. Fig. 1.21b. The perceptual sweet spot size as investigated by Frank [44] for SDM processed RIRs cover an area in IEM CUBE that increases with the SDM order N chosen (black = 5th, gray = 3rd, light gray = 1st order Ambisonics). In comparison to panned direct sound, one should keep some distance to the loudspeakers to avoid breakdown of ...
Context 39
... Green's function in three dimensions is derived in Appendix A.6.3, Eq. (A.91), For the phase approximation, for instance at a wave-length of 30 cm, we notice even for a relatively small distance difference, e.g. between 15 m and 15 m + 15 cm, we could change the sign of the wave. ...
Context 40
... spherical Bessel differential equation: spherical Hankel functions of the second kind h (2) n (kr) able to represent radiation (radially outgoing into every direction), consistently with Green's function G, diverging with an (n + 1)-fold pole at kr = 0, a physical behavior that would also be observed after spatially differentiating G, see Fig. 6.1; spherical Bessel functions j n (kr) = ℜ{h (2) n (kr)} are real-valued, converge everywhere, exhibit n (kr)} (top left), imaginary part of spherical Hankel functions ℑ{h (2) n (kr)} (top right), and magnitude/dB of |h (2) n (kr)| (bottom), over kr an n-fold zero at kr = 0, and can't represent radiation. Implementations typically rely ...
Context 41
... physical boundary of the rigid spherical surface is expressed as a vanishing radial component of the sound particle velocity. The radial sound particle velocity is obtained via the 13). This requires to evaluate differentiated spherical radial solutions j n (x) as well as h (2) n (x), which is implemented by f n (x) = n x f n (x) − f n+1 (x) for either of the functions, cf. ...
Context 42
... loud, so also diffuse-field equalization of the E measure is desirable in every band. To fulfill the above constraints, we propose to use the following set of FIR filter responses as given in [26,27], that are modified by a filter bank employing diffuse-field normalized max-r E -weights in separate frequency bands b = 0, . . . , N, cf. Fig. 6.11, with the nth order discarded for bands below b < ...
Context 43
... of a plane-wave sound pressure mapped to a directional Ambisonic signal becomes frequency-dependent as shown in Fig. 6.13, and it has minimal side lobes. 6 Higher-Order Ambisonic Microphones and the Wave Equation (Linear, Lossless) 32Hz 63Hz 125Hz 250Hz 500Hz 1kHz 2kHz 4kHz 8kHz -10dB 0dB 10dB 20dB 30dB n<1 n<2 n<3 n<4 n<5 n=0 n=1 n=2 n=3 n=4 Fig. 6.11 Filter-bank-regularized/dB over frequency/Hz, diffuse-field equalized max-r E weighted spherical microphone array responses using i n ρ n (ω) = N b=n a n,b H b (ω) (ka) 2 h Simulation is done with the order N sim = 30 and spatial aliasing will occur above 5.2 kHz. Gain matching was assumed to be up to < ±0.5 dB accurate; the map shows ...
Context 44
... gain match The effect on mapping is equivalent to one of microphone self noise, however gain mismatch yields a correlated signal exciting the microphones, whereas self-noise yields low-frequency noise. If regularization filters were set to 50, 160, 500, 1600 and sidelobe suppression turned off for testing, one would get the poor image as in Fig. 6.14a, where high-order signals at low frequencies are highly ...
Context 45
... a noise-free case is assumed, and only the max-r E side-lobe suppression of the highest band is used for all bands, one gets the image in Fig. 6.14b, which improves with individual max-r E weights in Fig. ...
Context 46
... 0dB 5dB 10dB 15dB 20dB 25dB Fig. 6.15 Self-noise modification |G(ω)| 2 /dB over frequency/Hz for the filter bank configurations using the cut on frequencies 2k, 3k, 4k, 5k (no noise amplification), 600, 2k, 3.5k, 4.2k (5 dB noise amplification), 280, 1.3k, 2.6k, 3.6k (10 dB noise amplification), 150, 950, 2k, 3.15k (15 dB noise amplification), and 90, 680, 1.65k, 2.6k (20 ...
Context 47
... He could show that the perceived distance between the listener and the higher-order directional source could not only be controlled by the order of the directivity pattern but also by the orientation of the source (towards the listener, away from the listener). Beams projecting sounds away from the listener were perceived behind the source, cf. Fig. 7.1. Again, the perceptual results could be modeled by simple measures known from room ...
Context 48
... study in [16] showed that distance control by changing the directivity and its orientation can also be achieved with the IKO in a real room, cf. Fig. 7.10. The experiments used stationary pink noise and could create auditory objects nearly 2 m behind the IKO, which corresponds to the distance between the IKO and the front wall of the playback ...
Context 49
... on the angle ϕ of the sound source. Equation (1.2) maps a single sound s from ϕ to the mid W and side Y signals by the gains [W, Y ] Decoding of MS signals to a stereo loudspeaker pair. Decoding of the mid-side signal pair to left and right loudspeaker is done by feeding both signals to both loudspeakers, however out-of-phase for the side signal, Fig. ...
Context 50
... width. Modifying the mid versus side signal balance before stereo playback, using a blending parameter α, allows to change the width of the stereo image from α = 0 (narrow) to α = 1 (full), Fig. 1.4a, see also ...
Context 51
... record the Ambisonic channels W, X, Y, one can use a Double-MS arrangement as shown in Fig. ...
Context 52
... -angled cardioids. Extending the MS scheme for recording with cardioid microphones, Fig. 1.3, cardioid microphones could be used to obtain the front-back and left-right figure-of-eight pickup patterns by corresponding pair-wise differences, and one omnidirectional pattern as their sum, Fig. 1.6. However, the use of 4 microphones for only 3 output signals is inefficient. Combining all the three microphone signals yields an ...
Context 53
... -angled cardioids. Extending the MS scheme for recording with cardioid microphones, Fig. 1.3, cardioid microphones could be used to obtain the front-back and left-right figure-of-eight pickup patterns by corresponding pair-wise differences, and one omnidirectional pattern as their sum, Fig. 1.6. However, the use of 4 microphones for only 3 output signals is inefficient. Combining all the three microphone signals yields an omnidirectional pickup pattern as N −1 k=0 cos(ϕ + 2π N k) = 0. Moreover introducing the differences between the front and two back microphone signals and between the left and right microphone signals yields ...
Context 54
... effect is important for head-tracked headphone playback to render the VR/360 • audio scene static around the listener. A complete playback system is shown in Fig. 1.9. The big advantage of such a system is that rotational updates can be done at high control rates and the HRIRs of the convolver are ...
Context 55
... pickup pattern aiming at θ 1 is described by , to produce the direction dipoles θ T X θ, 3D Ambisonic recording with a tetrahedral arrangement of cardioids. The principle that worked for three cardioid microphones on the horizon also works for a coincident tetrahedron microphone array of cardioids with the aiming directions FLU-FRD-BLD-BRU, see Fig. 1.11, and [12], Encoding is achieved there by the matrix that adds all microphone signals in the first line (W omnidirectional), subtracts back from front microphone signals in the second line (X figure-of-eight), subtracts right from left microphone signals in the third line (Y figure-of-eight), and subtracts down from up microphone ...
Context 56
... the matrix that adds all microphone signals in the first line (W omnidirectional), subtracts back from front microphone signals in the second line (X figure-of-eight), subtracts right from left microphone signals in the third line (Y figure-of-eight), and subtracts down from up microphone signals in the last line (Z figure-of-eight), see also As Fig. 1.12 shows, practical microphone layouts should be as closely spaced as possible. Nevertheless for high frequencies, the microphones cannot be considered coincident anymore, and besides a directional error, there will be a loss of presence in the diffuse field. Typically a shelving filter is used to slightly boost high ...
Context 57
... iemlib (free download within pure-data) Figure 1.13 gives an example for horizontal (2D) first-order Ambisonic panning, decoded to 4 loudspeaker and 2 headphone signals. ...
Context 58
... iemlib (free download within pure-data) Figure 1.13 gives an example for horizontal (2D) first-order Ambisonic panning, decoded to 4 loudspeaker and 2 headphone signals. Figure 1.14 shows the processing inside the Pd abstraction [FOA_binaural_decoder] contained in the Fig. 1.13 example, which uses SADIE database 1 subject 1 (KU100 dummy head) HRIRs to render headphone signals. ...
Context 59
... iemlib (free download within pure-data) Figure 1.13 gives an example for horizontal (2D) first-order Ambisonic panning, decoded to 4 loudspeaker and 2 headphone signals. Figure 1.14 shows the processing inside the Pd abstraction [FOA_binaural_decoder] contained in the Fig. 1.13 example, which uses SADIE database 1 subject 1 (KU100 dummy head) HRIRs to render headphone signals. Figure 1.15 sketches a first-order Ambisonic panning in 3D with decoding to an octahedral loudspeaker layout; master level [multiline∼] and hardware outlets [dac∼] were omitted for easier ...
Context 60
... 1.14 shows the processing inside the Pd abstraction [FOA_binaural_decoder] contained in the Fig. 1.13 example, which uses SADIE database 1 subject 1 (KU100 dummy head) HRIRs to render headphone signals. Figure 1.15 sketches a first-order Ambisonic panning in 3D with decoding to an octahedral loudspeaker layout; master level [multiline∼] and hardware outlets [dac∼] were omitted for easier readability. ...
Context 61
... source and importing a mono/stereo audio file (per drag-and-drop), the next step is the setup of the track channels. As shown in the table, the virtual source has a single-channel (mono) input and 4 output channels to send the 4 channels of first-order Ambisonics to the Master. The option to send to the Master is activated by default, cf. left in Fig. 1.16. The Master track itself requires 4 input channels and 6 output channels to feed the 6 loudspeakers (right). In Reaper, there is no separate adjustment for input and output channels, thus the Master track has to be set to 6 ...
Context 62
... the source track FX, the ambix_encoder_o1 can be used to encode the virtual source signal at an arbitrary location on a sphere by inserting the plug-in into the track of the virtual source, cf. its panning GUI in Fig. 1.17. For adding more sources, the track of the virtual source can simply be copied or duplicated. All effects and routing options are maintained for the new ...
Context 63
... the decoding matrix and its channel sequence and normalization. For the exemplary octahedral setup with 6 loudspeakers, the following text can be copied to a text file and saved as config-file, e.g., "octahedral.config". The decoder After loading the preset into the decoder plug-in, the decoder can generate the loudspeaker signals as shown in Fig. 1.18. In the example, the virtual source is panned to the front, resulting in the highest level for loudspeaker 1 (front). The loudspeaker 3 (back) is 12dB quieter because of a side-lobe suppressing super cardioid weighting implied by the switch /coeff_scale n3d, as a trick to keep things ...
Context 64
... shown on the SADIE-II website, 2 the SADIE-II head-related impulse responses can be used to rendering Ambisonics to headphones. The listing below shows a configuration file to be used with ambix_binaural, cf. Fig. 1.19, again using the trick to select n3d to keep the numbers simple and super-cardioid weighting #GLOBAL /coeff_scale n3d /coeff_seq acn #END #HRTF 44K_16bit/azi_0,0_ele_0,0.wav 44K_16bit/azi_90,0_ele_0,0.wav 44K_16bit/azi_180,0_ele_0,0.wav 44K_16bit/azi_270,0_ele_0,0.wav 44K_16bit/azi_0,0_ele_90,0.wav 44K_16bit/azi_0,0_ele_-90,0.wav ...
Context 65
... that delay-based stereophonic recording, such as AB, or equivalence-based recording, such as ORTF, INA5, etc., is often required and wellknown in its mapping properties for spaciousness and diffuseness, correspondingly. What is nice about higher-order Ambisonics: it can make use of these benefits by embedding such recordings appropriately, see Fig. ...
Context 66
... about higher orders: Ambisonics extended to higher orders permits a refinement of the directional resolution and hereby improves the mapping of uncorrelated sounds in playback. Figure 1.21a shows the correlation introduced in two neighboring loudspeaker signals when using Ambisonics, given their spacing of 60 • . ...
Context 67
... sounds in playback. Figure 1.21a shows the correlation introduced in two neighboring loudspeaker signals when using Ambisonics, given their spacing of 60 • . Given the just noticeable difference (JND) of the inter-aural cross correlation, the figure indicates that an Ambisonic order of ≥3 might be necessary to perceptually preserve decorrelation. Fig. 1.20 How is a microphone tree represented in Ambisonics, when it consist of 6 cardioids spaced by 60 cm and 60 • on a horizontal ring, and a ring of 4 super cardioids spaced by 40 cm and 90 • as height layer, pointing upwards? (b) Perceived depth in dependence of Ambisonics playback order for two listening positions (a) Inter-channel cross ...
Context 68
... this reason, the perception of spatial depth strongly improves when increasing the Ambisonic order from 1 up to 3, Fig. 1.21b. However, this is only the case when seated at the central listening position. Outside this sweet spot, higher orders than 3, e.g., 5, additionally improve the mapping of depth [19]. Therefore, higher-order Ambisonics is important for preserving spatial impressions and when supplying a large audience. Figure 1.22 shows that the ...
Context 69
... higher-order Ambisonics is important for preserving spatial impressions and when supplying a large audience. Figure 1.22 shows that the sweet area of perceptually plausible playback increases with the Ambisonic order [20]. With fifth-order Ambisonics, nearly all the area spanned by the horizontal loudspeakers at the IEM CUBE, the 12 × 10 m concert space at our lab, becomes a valid listening area. ...
Context 70
... Frank [10] investigated the auditory source width for frontal loudspeaker pairs with 0 dB level difference and various aperture angles, as well as the influence of an additional center loudspeaker on the auditory source width. The response was given by reading numbers off a left-right symmetric scale written on the loudspeaker arrangement ( Fig. 2.11). Figure 2.11 (right) shows the statistical analysis of the responses. Obviously the additional center loudspeaker decreases the auditory source ...
Context 71
... 2 Auditory Events of Multi-loudspeaker Playback Fig. 2.13 Model of the perceived width as 5 8 of the half-angle arccos r E matches the half-angle of the experiment. Except for a lower limit, which is determined by the apparent source width (ASW) due to the room acoustical setting For an additional center loudspeaker g 3 = 1, θ T = (1, 0), the estimator ...
Context 72
... compared to C, R. In order to avoid a strong increase in source width or annoying phasing effects, the outmost loudspeakers L and R are strongly reduced in their level, typically around -12dB compared to loudspeaker C. In doing so, the similarity of the comb filters yields barely any coloration when moving a source between the two directions, cf. Fig. ...
Context 73
... Correspondingly, the perceived directions shown in the gray 5 • -histogram bubbles of Fig. 3.7 indicate the perceived directions when the listener is located left-shifted off-center. While localization is slightly attracted by the closer loudspeaker at 0 • , the larger spread causes a more monotonic outcome that is less split than with VBAP in Fig. ...
Context 74
... well would diffuse signals be preserved played back? All the above experiments deal with how non-diffuse signals are presented. To complement what is shown in Fig. 1.21 of Chap. 1 with an explanation, the relation between Ambisonic order and its ability to preserve diffuse fields is estimated here by the covariance between uncorrelated directions. Assume a max-r E -weighted Nth-order Ambisonic panning function g(θ T s θ ) that is normalized to g(1) = 1, encodes two sounds s 1,2 from two directions ...
Context 75
... result was presented in Fig. 1.21 and was used to argue that the directional separation of first-order Ambisonics by its high crosstalk term g 12 might be too weak. Higher-order Ambisonics decreases this directional crosstalk and therefore improves the representation of diffuse sound ...
Context 76
... pre-calculated. Note the similarity to the first-order 2D example of Fig. 1.13, to which the main change is the use of the circular harmonics matrix ...
Context 77
... decoding to headphones, programming in Pd also looks rather similar as in the first-order example in Fig. 1 loudspeaker positions need to be employed. To work in 3 dimensions, programming in Pd would also be similar as in the corresponding first-order example of Fig. 1.15, using the matrix object [mtx_spherical_harmonics]. Typically, pre-calculated decoders including AllRAD and max-r E are used and loaded by, e.g., [mtx D.mtx] into Pd to ...
Context 78
... decoding to headphones, programming in Pd also looks rather similar as in the first-order example in Fig. 1 loudspeaker positions need to be employed. To work in 3 dimensions, programming in Pd would also be similar as in the corresponding first-order example of Fig. 1.15, using the matrix object [mtx_spherical_harmonics]. Typically, pre-calculated decoders including AllRAD and max-r E are used and loaded by, e.g., [mtx D.mtx] into Pd to keep programming ...
Context 79
... typical audio processing steps for Ambisonic surround-sound signal manipulation are shown in the block diagram Fig. 5.1 from [2]. The description of the multi-venue application in [3] and one for live effects [4] might be ...
Context 80
... are two ways of employing parametric equalizers to Ambisonic channels. Either a single-/multi-channel input of a mono-encoder or a multiple-input encoder is filtered by parametric equalizers. Or each of the Ambisonic signal's channels is filtered by the same parametric equalizer, see Fig. 5.11a. Fig. 5.11 Block diagram of processing that commonly and equally affects all Ambisonic signals, such as parametric equalization and dynamic processing (compression), without recombining the signals Bass management is often important to not overdrive smaller loudspeaker systems of, e.g., a 5th-order hemispherical playback system with ...
Context 81
... are two ways of employing parametric equalizers to Ambisonic channels. Either a single-/multi-channel input of a mono-encoder or a multiple-input encoder is filtered by parametric equalizers. Or each of the Ambisonic signal's channels is filtered by the same parametric equalizer, see Fig. 5.11a. Fig. 5.11 Block diagram of processing that commonly and equally affects all Ambisonic signals, such as parametric equalization and dynamic processing (compression), without recombining the signals Bass management is often important to not overdrive smaller loudspeaker systems of, e.g., a 5th-order hemispherical playback system with subwoofer ...
Context 82
... signal was speech and as a reference it used the frontal loudspeaker with the unprocessed signal "REF". The experiment tested the algorithm with both the symmetric impulse responses suggested by Eq. (5.18), and such truncated to their causal q ≥ 0-side, for a listening position at the center of the arrangement (bullet marker) and at 1.25 m shifted to the right, off-center (square marker). Figure 5.12 indicates for the widening algorithm with τ = 1.5 ms that the perceived width saturates above N > 2 at both listening positions. ...
Context 83
... to their causal q ≥ 0-side, for a listening position at the center of the arrangement (bullet marker) and at 1.25 m shifted to the right, off-center (square marker). Figure 5.12 indicates for the widening algorithm with τ = 1.5 ms that the perceived width saturates above N > 2 at both listening positions. Despite the effect of the causal-sided Fig. 5.12 Perceived width (left) and audio quality (right) of frequency-dependent dispersive Ambisonic rotation as widening effect using the setting τ = 1.5 ms, the Ambisonic orders N = 1, 2, 3, 5, and L = 3, 4, 5, 7 loudspeakers on the frontal semi-circle, with listening positions at the center (bullet marker) and half-way right off-center ...
Context 84
... Perceived width (left) and audio quality (right) of frequency-dependent dispersive Ambisonic rotation as widening effect using the setting τ = 1.5 ms, the Ambisonic orders N = 1, 2, 3, 5, and L = 3, 4, 5, 7 loudspeakers on the frontal semi-circle, with listening positions at the center (bullet marker) and half-way right off-center (square marker) Fig. 5.13 Perceived width (left) and audio quality (right) of frequency-dependent dispersive Ambisonic rotation as distance/diffuseness effect using the setting τ = 15 ms, the Ambisonic orders N = 1, 2, 3, 5, and L = 3, 4, 5, 7 loudspeakers on the frontal semi-circle, with listening positions at the center (bullet marker) and half-way right ...
Context 85
... more pronounced preference of the causal-sided implementation in terms of audio quality is found in Fig. 5.13 for the setting τ = 15 ms, where the algorithm is increasing the diffuseness or perceived distance for orders N > 2 at both listening ...
Context 86
... nearest loudspeakers. One can observe that rendering diffuse reverberation for a large audience benefits from a high Ambisonic order. Moreover, experiments in [43] revealed an improvement of the perceived spatial depth mapping, i.e. a clearer separation between foreground and background sound for the SDM-processed higher-order reverberation, cf. Fig. 1.21b. The perceptual sweet spot size as investigated by Frank [44] for SDM processed RIRs cover an area in IEM CUBE that increases with the SDM order N chosen (black = 5th, gray = 3rd, light gray = 1st order Ambisonics). In comparison to panned direct sound, one should keep some distance to the loudspeakers to avoid breakdown of ...
Context 87
... Green's function in three dimensions is derived in Appendix A.6.3, Eq. (A.91), For the phase approximation, for instance at a wave-length of 30 cm, we notice even for a relatively small distance difference, e.g. between 15 m and 15 m + 15 cm, we could change the sign of the wave. ...
Context 88
... spherical Bessel differential equation: spherical Hankel functions of the second kind h (2) n (kr) able to represent radiation (radially outgoing into every direction), consistently with Green's function G, diverging with an (n + 1)-fold pole at kr = 0, a physical behavior that would also be observed after spatially differentiating G, see Fig. 6.1; spherical Bessel functions j n (kr) = ℜ{h (2) n (kr)} are real-valued, converge everywhere, exhibit n (kr)} (top left), imaginary part of spherical Hankel functions ℑ{h (2) n (kr)} (top right), and magnitude/dB of |h (2) n (kr)| (bottom), over kr an n-fold zero at kr = 0, and can't represent radiation. Implementations typically rely ...
Context 89
... physical boundary of the rigid spherical surface is expressed as a vanishing radial component of the sound particle velocity. The radial sound particle velocity is obtained via the 13). This requires to evaluate differentiated spherical radial solutions j n (x) as well as h (2) n (x), which is implemented by f n (x) = n x f n (x) − f n+1 (x) for either of the functions, cf. ...
Context 90
... loud, so also diffuse-field equalization of the E measure is desirable in every band. To fulfill the above constraints, we propose to use the following set of FIR filter responses as given in [26,27], that are modified by a filter bank employing diffuse-field normalized max-r E -weights in separate frequency bands b = 0, . . . , N, cf. Fig. 6.11, with the nth order discarded for bands below b < ...
Context 91
... of a plane-wave sound pressure mapped to a directional Ambisonic signal becomes frequency-dependent as shown in Fig. 6.13, and it has minimal side lobes. 6 Higher-Order Ambisonic Microphones and the Wave Equation (Linear, Lossless) 32Hz 63Hz 125Hz 250Hz 500Hz 1kHz 2kHz 4kHz 8kHz -10dB 0dB 10dB 20dB 30dB n<1 n<2 n<3 n<4 n<5 n=0 n=1 n=2 n=3 n=4 Fig. 6.11 Filter-bank-regularized/dB over frequency/Hz, diffuse-field equalized max-r E weighted spherical microphone array responses using i n ρ n (ω) = N b=n a n,b H b (ω) (ka) 2 h Simulation is done with the order N sim = 30 and spatial aliasing will occur above 5.2 kHz. Gain matching was assumed to be up to < ±0.5 dB accurate; the map shows ...
Context 92
... gain match The effect on mapping is equivalent to one of microphone self noise, however gain mismatch yields a correlated signal exciting the microphones, whereas self-noise yields low-frequency noise. If regularization filters were set to 50, 160, 500, 1600 and sidelobe suppression turned off for testing, one would get the poor image as in Fig. 6.14a, where high-order signals at low frequencies are highly ...
Context 93
... a noise-free case is assumed, and only the max-r E side-lobe suppression of the highest band is used for all bands, one gets the image in Fig. 6.14b, which improves with individual max-r E weights in Fig. ...
Context 94
... 0dB 5dB 10dB 15dB 20dB 25dB Fig. 6.15 Self-noise modification |G(ω)| 2 /dB over frequency/Hz for the filter bank configurations using the cut on frequencies 2k, 3k, 4k, 5k (no noise amplification), 600, 2k, 3.5k, 4.2k (5 dB noise amplification), 280, 1.3k, 2.6k, 3.6k (10 dB noise amplification), 150, 950, 2k, 3.15k (15 dB noise amplification), and 90, 680, 1.65k, 2.6k (20 ...
Context 95
... He could show that the perceived distance between the listener and the higher-order directional source could not only be controlled by the order of the directivity pattern but also by the orientation of the source (towards the listener, away from the listener). Beams projecting sounds away from the listener were perceived behind the source, cf. Fig. 7.1. Again, the perceptual results could be modeled by simple measures known from room ...
Context 96
... study in [16] showed that distance control by changing the directivity and its orientation can also be achieved with the IKO in a real room, cf. Fig. 7.10. The experiments used stationary pink noise and could create auditory objects nearly 2 m behind the IKO, which corresponds to the distance between the IKO and the front wall of the playback ...
Citations
... Immersive virtual environments can be used to experience 3D visualizations with the aim of providing a more realistic experience by surrounding users with stimuli such as audio stimuli. Despite research primarily focusing on the spatial fidelity of multi-loudspeaker playback, the overall quality of surround sound playback was found to be largely determined by timbral fidelity (Zotter & Frank, 2019). The animation toolkit in SolidWorks was used to create the motion of robotics by adding motors at each joint of the robot to simulate movements. ...
Manufacturing applications of virtual reality (VR) technology are growing. The challenge is to design, integrate, and evaluate VR simulation for manufacturing Systems that improves the effectiveness of the planning process. In this paper, we discuss the technical infrastructure necessary to design a collaborative virtual manufacturing planning system. We describe the VR system setup and the integration of hardware and software to produce high-fidelity virtual simulation for manufacturing planning purposes. The designing guidelines are demonstrated by a high-fidelity VR simulation of a stamping process. The VR simulation also presents a method of visualizing computer-aided engineering content. Also, this paper assesses the factors that affect overall fidelity of the VR simulation. Objective evaluation of the VR simulation was conducted using the fidelity framework and the scales, whereas the subjective evaluation methods used were VR-simulation-driven data interpretation. The VR simulation was evaluated by a selective sample of 33 senior engineering students using a highly reliable scale (Cronbach’s Alpha = .93) questionnaire that was designed to evaluate functionality, performance, and experience. The results of the subjective evaluation validate the evaluation of objective scales to be high-medium for the VR system used (M = 5.24, M = 5.11) respectively. Significant positive relationships were found between all factors, except distraction, which had a significant negative relationship with fidelity. Overall, the realism and sensory systems factors were found to be the main significant factors affecting the fidelity of the VR system.
