Demonstrator pipe organ by Principal Pipe Organs of York, UK consisting of a pipe for one note (G4) of each of the following stops labelled numerically: (1) Open Diapason 8’, (2) Principal 4’, (3) Twelfth 2 2 / 3 ’, (4) Fifteenth 2’, (5) Tierce 1 3 / 5 ’, (6) Larigot 1 1/3’, (7) Septième 1 1 / 7 , (8) Octavin 1’, (9) Hohl Flute 8’, (10) Block Flute 4’, (11) Piccolo 2’, (12) Salicional 8’, 

Context in source publication

Context 1

... to the sound modifier tubes. The VTM-10 kit sound modifiers are provided in two forms as follows. There are five acrylic tubes representing in cylindrical cross-section the oral tract for the vowels /i/, /e/, /a/, /o/ and /u/ with hard rubber couplers to connect either of the two sound sources. In addition, there is a set of acrylic squares with central holes of various diameters and these can be placed together on a special frame to enable other vocal tract shapes to be made up. This too has a hard rubber coupler to link it to either of the two sound sources. Arai [8] also proposes the use of a horn loudspeaker driver unit and he provides a description of a suitable design for a hard rubber coupler, so that it can be used as an electrical driver to enable any signal to be used as excitation such as a pulse train, white noise or the L/F source model [9] that is commonly found in practical electronic synthesis systems such as the Klatt synthesizer [10]. Three oral tract tubes and the sound sources from the VMT-10 kit are shown in figure 1a. A rather crude power source and sound source model can be fashioned out of a two litre plastic drinks bottle, three plastic sandwich bags, plastic insulating tape, plastic tubing with a “T” piece and a whistle-type artificial larynx from the VTM-10 kit [8]. The “T” piece is fitted to the end of the plastic tube and a plastic sandwich bag is fitted on each of the two branches of the “T” to be airtight. These are the “lungs”. The bottom of the bottle is cut off and its screw-top is removed. A hole is made through the screw-top that will be a snug fit for the plastic tube. The top is screwed back onto the bottle and the tube with the “T” piece and bags attached is drawn through the lid until the “T” piece and bags are in the middle of the bottle. The third plastic bag, which will be the “diaphragm” is fitted around the bottom of the bottle and taped in place such that it is very loose but airtight. The top of the bottle is unscrewed a little and the diaphragm is pushed into the bottom of the bottle and the top is tightened. This is the “raised diaphragm” position. The “lungs” should be deflated by sucking on the end of the plastic tube, and then the artificial larynx is fixed to the far end of the tube, outside the bottle. The lung model is shown in figure 1b. Breathing in is achieved by gently grasping the centre of the “diaphragm” and pulling it gently away from the bottle. The “lungs” should inflate”. On breathing out by pushing the “diaphragm” into the bottom of the bottle, a sound is heard from the artificial larynx. A hose from the oil heat exchanger from a Toyota 4by4 vehicle is about the right diameter for a fully open vocal tract and it also has a curve in it or about the right radius for the oral cavity. When placed over a small loudspeaker unit that includes a suitable electronic oscillator (pulse-like wave shape with amplitude and f0 control (varying between approximately 80 to 400 Hz), the effects of the sound source and sound modifiers can be demonstrated. A duck call makes a good sound source and a 17.5 cm piece of soft-walled rubber tubing fitted over the end provides a demonstration vocal tract. Both are shown in figure 1b. A tilting paper larynx model can be made by following on-line instructions [11] and this design has been used for a tilting aluminium version that is around 25cm tall onto which rubber bands can be fixed to show how the vocal folds are stretched as the larynx is tilted (see figure 1c). Medical models of the lungs, bronchi, larynx, vocal tract and cut-away details of the head can be used to enhance understanding of human voice production in a graphical and hands-on manner. A replica by Principal Pipe Organs of York, UK of the von Kempelin [12] speaking machine of 1793 (figure 1d) is very useful as a voice production demonstration device not only because for its historical interest, but also because it is visually rather appealing as a model of the power source, sound source and sound modifiers. Harmonic synthesis can be readily demonstrated on a computer using a freeware resource such as Pure Data, or PD , [13] or with a purpose-implemented iPad Application such as “Harmonic Synthesis” [14], but the use of organ pipes makes for a much more physical and tangible acoustic experience. A pipe organ is an acoustic harmonic synthesizer. The stops on an organ enable the player to create different sounds through harmonic synthesis, since the majority of the stops themselves are directly related to harmonics. Most of the stops have a footage associated with them which indicates the pitch at which that particular rank of pipes plays in relation to the overall f0 of the sound. A stop with an 8 on it indicates that the pipe for the lowest note (two octaves below middle C - the bottom note on an organ keyboard) is approximately 8 feet long, and such a stop plays at concert pitch. In other words, the notes sound at the same pitch as the piano. Figure 2 shows a pipe organ demonstrator built by Principal Pipe Organs of York, UK for a single note which has 16 stops with one pipe for each stop. It is designed to demonstrate different types of organ pipes and acoustic synthesis using harmonics 1-8. There are two main types of organs pipe: flues and reeds. The demonstrator has 13 flue pipes (harmonics 1-8 based essentially on principal pipes, harmonics 1-3 based on stopped flute pipes, and two pipes that are slightly de-tuned to create a string sound – Salicional and Voix Celeste ) and three reed pipes (oboe, trumpet and cornopean). The principal and string pipes are open and the flute pipes are closed (the stoppers in their ends are visible in the figure). Each pipe can be played separately or in any combination by means of small brass buttons. Work with the cup and string communicator offers an opportunity to illustrate the potential for disruption due to competing acoustic noise and the acoustics of the space. If a class is trying to communicate a message using this system and they are all in the same room, preferably a reverberant hall, then the speakers will end up raising their voices in order to be heard. Thus the background noise will be increased to a high level and the point can be made that this is something of a vicious circle – one speaker’s voice is raised increasing the noise level for everyone else so other speakers do so too and the level rises to an equilibrium level of sorts where speakers are shouting. At this point, it is perhaps worth pointing out that the cup and string can potentially become redundant because the source level is high enough to be heard without it if it weren’t for the background noise and room reverberation. Room reverberation can be isolated by listening to a hand clap which offers an opportunity for explaining the importance of careful listening and the use of an impulse (hand clap) to test informally the acoustics of spaces. The effect can be enhanced in terms of level by organising the group to clap in unison together after, say, a count of three. This develops coordination skills, group effort and a useful musical skill. It is worth noting that many singers, speakers and musicians, use a hand clap to test the acoustics of performance spaces during rehearsals to determine good performance positions, and these are not always centre stage or behind a speaker’s lectern [6]. The presence of background noise and the effects of room acoustics are good examples of interfering unwanted signals for a communication system. To make the effects of these even more pronounced practically with a group studying a foreign language, set up the cup and string pairs down the long axis of a room. Those at one end of the room will be the speakers and those at the other end will be the listeners. The speakers will be given a message on paper which the listeners have to write down. What you do not tell them is that the messages are in another language, albeit but one that they are studying. Use has been made of French and Latin phrases in this way in a local school where these languages are studied (the messages were composed by one of their teachers to ensure that it would be well within the capabilities of the pupils to understand and translate the sentences). Insist that all communication between the speakers and listeners must be done using the cup and string apparatus and give out the messages. The background noise tends to rise extremely quickly during these sessions and many attempts are required before the listeners receive a useful message. Swap speakers and listeners and give out another set of messages again in the foreign language and the task is completed more quickly. To end, bring the group together, preferably with the teacher who wrote the sentences present, and ask each to read out the message they received as listener and offer a translation. Ask the speaker to confirm or otherwise the message content and translation (the teacher may well intervene at this point!). Typically for the first group of listeners, the heard versions are incomplete sentences. Indeed, on one occasion a Latin transmitted sentence was received as a French sentence! Here are some example sentences and their translations in ...