WO2004025988A1

WO2004025988A1 - Microphone system for accordions

Info

Publication number: WO2004025988A1
Application number: PCT/AU2003/001169
Authority: WO
Inventors: Peter Raymond Anderson
Original assignee: Peter Raymond Anderson
Priority date: 2002-09-10
Filing date: 2003-09-09
Publication date: 2004-03-25
Also published as: AU2002951361A0

Abstract

A microphone arrangement, for amplifying the sounds produced by an accordion, includes a keyboard pickup, a reed pickup and a bass pickup. The keyboard pickup (10) comprises a body (12) formed from a piece of sound transmitting material (14) such as dense closed cell ethyl vinyl acetate foam, and a contoured base member (16), between which material (14) and which base member (16) a sealed chamber (18) is created. An electret microphone (20) is located in the chamber (18). The contour of the base member (16) is ribbed, having peaks and valleys, the chamber (18) being created by filling in some of the valleys and cutting gaps in some of the peaks.

Description

MICROPHONE SYSTEM FOR ACCORDIONS

This invention relates to a microphone arrangement for musical instruments such as accordions.

At the present time it is often necessary to provide microphones or pickups for "acoustic" musical instruments being played "live", in order for the sounds made by those instruments to be amplified for the benefit of an audience.

Difficulties have arisen when attempts have been made to amplify sounds produced by an accordion. Accordionists the world over are forever beset with difficulties in getting their instrument to sound correct and true when played on stage through a public address or other form of sound system. This is particularly the case when the stage is shared by the accordionist with loud instruments such as drums and electric guitars.

Most other instruments have their amplification techniques well sorted out. Wind instruments generally have their sound emanating from a singe point, and a suitably placed microphone works well. Stringed instruments such as guitars and violins transmit all the sound of the strings through one point - the bridge - and a piezo-ceramic pickup is usually used. This is now tried and true technology. The accordion, however, produces its sound differently and the amplification technology has so far not reached a very refined state.

Each key on an accordion activates sound from up to five vibrating metal reeds and the sound produced from the keyboard end can emanate from any point in an area typically 40cm x 15cm. The bass end makes it effectively two instruments joined together, and the amplification of the bass end has its own problems.

The difficulty in amplifying accordion sounds is in providing a microphone system that will pick up sound from the aforementioned 40cm x 15cm area, yet will be close enough to the sound sources (the reeds) that other on-stage noise sources such as drums, will not unduly spill into and be detected by the accordion microphone system. For the sake of neatness and proximity, microphones are best mounted on the inside of the grille of an accordion. The grille is that component of an accordion which covers the sound sources and mechanism, but allows the instrument's sound to pass through. Two types of microphone have been used in this way.

Firstly, crystal microphones, old fashioned microphones, have been used. Usually three or four crystal microphones were mounted inside an accordion grille. They resemble a microphone from an old telephone and the clarity of sound produced can also be likened to that of an old telephone. Secondly, electret microphones may be used. They are modern and cheap (typically $3) and have a good frequency response. Current installations typically mount four to six of these inside an accordion grille. However, they do not handle well the sound pressure created by the reeds.

An accordion's sound source, the free reed, produces an acoustic waveform which is anything but sinusoidal. It is full of all sorts of spiky harmonics. Further, accordions tend to use combinations of reeds to generate their sound. For instance, the musette tuning has three reeds playing almost the same pitch to give a 'double tremolo' sound. The high frequency spikes on the single reed waveform, when sat atop a fundamental frequency wave which sits atop a low frequency double tremolo wave, reach very high dB levels indeed. Thus, the sound pressure can be very high.

The grille of the accordion is used to 'soften' the instrument's sound. The upper mid frequencies, say 3kHz to 7kHz, or the 'nasty' part of an accordion sound, are much stronger on the inside of the grille than on the outside. An electret microphone (and nearly any other microphone) is very likely to audibly distort when mounted on the inside of the grille of a musette accordion playing adjacent semitones at full volume.

For the aforementioned reasons, a satisfactory arrangement for amplifying instruments such as accordions has not been developed. In US-A-4,837,836, there is described a microphone pickup system in which a microphone is located inside a body having a generally rectangular cross-section, the microphone communicating with a sound groove extending along one face of the body. A rigid plate attached to that face defines with the body and the groove an elongated chamber having two open ends. The module is adapted to be located, for an accordion, along one of the three treble reed banks of the accordion.

It is believed that the arrangement of the US-A-4,837,836 has never been available to the public, and it is considered that that may be because the arrangement would not satisfactorily reproduce the sounds of an accordion, and could not cope with the sound pressures found within an accordion.

It is an object of this invention to provide an improved microphone, pickup or the like arrangement for the amplification of sounds produced by a musical instrument.

The invention provides a microphone arrangement for musical instruments such as accordions, characterised by a closed or sealed chamber in which or in communication with which is microphone means, and by a material, through which sounds from said instrument are adapted to pass to reach said chamber and said microphone.

The invention also provides an arrangement for picking up sounds produced by a musical instrument such as an accordion, said arrangement including means through which said sounds may travel, which means is adapted to attenuate said sounds to a predetermined degree, said sounds thereafter reaching a closed chamber in which, or in communication with which, is located microphone means.

The invention further provides a method suitable for amplifying sounds produced by a musical instrument such as an accordion, characterised by the step of: locating in, or near said instrument a pickup module in which microphone means picks up said sounds from a closed chamber, after they have passed through a medium which may attenuate said sounds to some degree.

The invention also provides a microphone or pickup arrangement for picking up sounds from the bass end of musical instruments such as accordions, characterised by microphone means located within a sheath of a first material, and by a second material interposed within said sheath and at least partially surrounding said microphone means, such that said first material and said second material are located between the source of said sounds.

Embodiments of the invention will be described in detail hereinafter, with reference to the accompanying drawings, in which:-

Fig. 1 is a side elevation of a simple form of microphone arrangement in accordance with the present invention;

Fig. 2 is a perspective view of a more complex embodiment of microphone arrangement according to the present invention;

Fig. 3 is a cutaway view of the embodiment of Fig. 2;

Fig. 4 is a perspective view of an embodiment of a microphone arrangement according to the present invention, suitable for reproducing the base reed area of an accordion;

Fig. 5 is a cross-sectional side elevation of the embodiment of Fig. 4;

Fig. 6 is an exemplary circuit diagram for an embodiment of a microphone arrangement according to the present invention;

Fig. 7 is a perspective view of an embodiment of a microphone arrangement according to the present invention, suitable for external mounting on an accordion;

Fig. 8 is a cross-section through the arrangement of Fig. 7;

Fig. 9 is a perspective view of a slimmer alternative microphone arrangement to that of Figs. 2 and 3, suitable for internal mounting on an accordion;

Fig. 10 is a cross-section through the arrangement of Fig. 9;

Fig 11 is a perspective view of an alternative embodiment to that of Fig 2; Fig. 12 is a diagrammatic cutaway view of the embodiment of Fig. 12;

Fig. 13 is a sectioned side elevation of an alternative embodiment to that of Fig. 5;

Fig. 14 is an alternative circuit for an accordion having grille and bass electret microphones;

Fig. 15 is a plan view of a circuit board embodying the bass pickup part of the circuit of Fig. 14; and

Fig. 16 is a plan view of a circuit board embodying the keyboard part of the circuit of Fig. 14.

The present invention is a microphone or pickup system designed to provide a large sound detecting surface in situations where multiple and separate sound sources need to be picked up and amplified evenly. The system has been designed to provide reliable amplification for performers who play in ensemble situations or in bands where the present generation of accordion pickups have proved to be totally inadequate in competing with other amplified instruments without enormous difficulties due to feedback. The basic principle is described in relation to Figs. 1 and 2, and is described as follows.

The microphone arrangement 10 may take the form of a cuboidal body 12. The body 12 is formed from a piece of sound transmitting material 14 having a cuboidal shape. The material 14 defines, with a base member 16, a chamber 18. A microphone 20 is located inside the chamber 18 or such that it communicates with the chamber 18. The chamber 18 is preferably a sealed chamber, with tape 22 or the like being used to cover the sides and ends of the join between the medium 14 and the base 16.

Preferably, the material of the medium 14 is a dense closed cell EVA (ethyl vinyl acetate) foam, more preferably the EVA foam available under the trade mark

Plastizoat. Plastizoat is generally used for orthopaedic work in splints, braces and the like. Preferably, the base member 16 is matting, more preferably rubber matting, and even more preferably 'pyramid contour' rubber matting, as shown in Fig. 2. Ideally, the medium 14 is affixed to the member 16, by being glued or adhered thereto. Preferably, the medium 14 is glued or adhered by being so glued or adhered to the peaks of the pyramid contour.

Pyramid contour rubber matting has been used in the prototype of Figs. 2 and 3 at least in part because of the difficulty in creating a uniform chamber by providing a groove in material 14. It is desirable that the chamber 18 be substantially of uniform height and substantially of uniform volume per unit length. The pyramid contour matting satisfies those criteria, and also acts well as a base member 16 to which the material 14 may be attached. It is also readily available. However, other configurations may be used which may also provide a satisfactory chamber 18. For example, columns other than pyramid-shaped columns could be used. Such columns may be cylindrical, rectangular or any other suitable shape. They may be tapered. The prototype of Figs. 2 and 3 works well to noticeably attenuate sounds produced by the accordion at distances greater than 7cm from microphone 20. It may well be that in a production model, the columns may not be equally spaced between the base member 16 and the material 14, but may form a pattern where they are more densely grouped in one area, such as near microphone 20, and/or may be larger, for example thicker, in such an area.

The dimensions of a working prototype of the embodiment of Figs. 1 and 2 are width 25mm and length 75mm or 175mm. The height of the medium 14 is 10mm, and of the matting 16 4mm. Thus it can be seen that the arrangement 10 is elongated in appearance. The microphone 20 may be sealed into the medium 14 by beeswax or the like, and its electric wiring 24 may exit from the top of the body 10, as shown in Fig. 2. Preferably, the microphone 20 is an electret microphone.

If the sound transmitting medium 14 is selected as appropriate for the job, one or more sound sources (for example, A, B and C in Fig. 1) acting upon the sound transmitting medium 14 will flow through the medium 14 and enter the chamber 18. The microphone 20 inside the chamber 18 will then pick up the sound sources with a relationship dependent on the intensity of the sound which would have appeared at the microphone 20 itself were it freely mounted. The task for which the microphone of the present invention (sometimes referred to as the Virtual Diaphragm Microphone or VDM) has been developed is the onstage amplification of the musical instrument known as the accordion. Of course, it may be suitable for other applications, not only in the area of musical instruments; for instance a spherical VDM could be used to monitor the behaviour of insects in a nest.

The microphone arrangement of the present invention in its application to the accordion has been developed to -

A. Fit inside the grille of most accordions, or when this is not possible to be mounted externally to the grille.

B. Pick up sound evenly across the aforementioned 40cm x 15cm area.

C. Use as its basis the cheap and clean sounding electret microphone 20.

D. Reduce sound pressure at the electret microphone 20 to levels which it can handle. E. Filter out upper mid frequencies to leave an end resultant sound which is both warm and crisp, but not harsh.

Many parameters affect the performance of the microphone arrangement of the present invention. These include:-

1. The volume and shape of the chamber 18. 2. The quality and characteristics of the microphone 20.

3. The mounting of the arrangement to the grille - whether it is mounted solidly or loosely. It is preferred that it be mounted solidly.

4. The surface consistency of the foam 14 (if foam is used). It has been found that a surface roughened by sandpaper reduces upper mid frequency response. A melted surface (material held over a flame) enhances upper mid frequency response. A cut surface is somewhere in between.

5. The shape of the sound transmitting material 14. 6. The size of the unit 10.

All these parameters are there to be adjusted, but the prototype of Figs. 2 and 3 works very well. For a small accordion, one microphone arrangement of the Fig. 2/Fig.3 type is sufficient. For a full sized accordion, two are recommended.

Despite the fact that the Figs. 2 and 3 prototype works well, it does have some drawbacks. For example, the use of the tape 22 to seal the sides of the arrangement 10 would probably be too labour-intensive for actual production of microphone pickup modules. Also, the prototype is a little thick for mounting on the inside of most accordions. That is why the embodiment of Figs. 9 and 10, to be described in detail hereinafter, was designed.

For mounting on the exterior of the grille of an accordion, it is best not to have the foam material 14 in contact with the grille; there is too much mechanical noise from the keyboard and other sources, which is picked up by the microphone 20. That is why the embodiment of Figs. 7 and 8, to be described in detail hereinafter, was designed.

The bass end of the accordion has so far received only a cursory mention, but its amplification presents a different series of problems. The bass end of an accordion plays bass notes and chords to accompany the more melodic keyboard end. It is possible to have as many as fourteen (14) reeds playing simultaneously, spanning a range of 5 octaves. Further, the bass reeds play into a largish chamber before the sound produced by the reeds finds its way out of the accordion. This chamber is the best place to locate a microphone, but sound pressures within it can be extremely high. The chamber does present the advantage that an even response can be obtained by a single microphone located within the chamber. Frequency response (40hZ to 10khZ is good) and sound pressure are the issues. For this application the combination of an electret microphone such as microphone 20 of Figs. 2 and 3 and a medium such as medium 14 of Figs. 2 and 3 is used to created another embodiment of microphone arrangement, that shown in Figs. 4 and 5. The embodiment of Figs. 4 and 5 may be referred to in this document as a Contact/Acoustic Microphone (CAM). The CAM arrangement 26 of Figs. 4 and 5 includes a hollow open-ended body or sheathing 28, which is preferably formed from a material such as plastic heat- shrink tubing. The body 28 is generally substantially cylindrical in shape, with a front end 30 preferably tapering to an opening 32. The rear end 34 of the body 28 has an opening 36 for the exit of wires 24 leading from a microphone 20, which is preferably an electret microphone.

Within the body 28, there is located toward the rear a microphone 20, which is lodged in a recess within a block of material 38, such that the microphone 20 is located between the bulk of material 38 and end 34 of body 28. Sealing material 44, for example beeswax, is located around wiring 24 to seal opening 36. Material 38, which preferably occupies the interior of the generally cylindrical portion of body 28, as shown in Fig. 5. Pinholes 40 provide access through body/sheathing 28 to the material 38. Mounting feet 42, which may also be formed from a dense closed cell foam, more preferably an EVA foam such as Plastizoat, are located on the base of arrangement 26. The arrangement is secured in place, for example to the bass board of the accordion, by glueing the feet 42 thereto.

The electret microphone 20 is well insulated by the combination of the Plastizoat and the heat-shrink plastic, and in that way copes with the sound pressure in the bass chamber of an accordion. The arrangement 26 picks up the very lowest notes by transmitted vibration. High frequencies are passed to the electret microphone 20 via the pinholes 40 in the sheathing 28 surrounding the material 38. Mid range frequencies (largely unwanted) are picked up by the end of the material 38 opposite the microphone 20. The hollow portion within the tapered section 30 of the sheathing 28 is intended to reduce mid range response. It is felt that that portion should be open-ended to prevent the development of standing waves within the material 38. This microphone 20 has a very good low frequency response with minimal chance of feedback and enough upper mid range response to give the bass end of the accordion both depth and attack, without being so strong in the mid range as to overpower the music being played on the keyboard end. A prototype of the arrangement 26 of Figs. 4 and 5 has the dimensions: length 100mm, with the length of material 38 60mm. The diameter of the body 28 is 25mm, and that of the microphone is 9mm.

Fig. 6 is an exemplary circuit diagram which may be used such that the arrangements of Figs. 1 to 5 work. It will be noted that the circuit of Fig. 6 carries out further filtering of unwanted frequencies.

The arrangement 46 of Figs. 7 and 8 is intended to be an alternative to that of Figs. 2 and 3, and is particularly suitable for external mounting on an accordion.

In arrangement 46, the material 14 and base member 16 are encased in and held together by heat-shrink or shrink-wrap plastic 48. Such plastic may only extend around the sides and top of the arrangement 46, but not over the ends, such as shown at 50. The ends, such as 50, may be sealed by wax such as beeswax, silicone rubber, or in any suitable manner.

As may be seen in Fig. 8, the wrapping 48 is removed from most of the top of the foam material 14. However, turned-over edges 52 are left to provide a non-foam mating surface for attachment of arrangement 46 to the exterior of the grille of an accordion. The wiring 24 from electret microphone 20 is arranged to exit through the side of sheathing 48.

The dimensions of the prototype of Figs. 7 and 8 are: length 175mm, height 17mm, and width 25mm.

Figs. 9 and 10 show a "slimline" microphone pickup arrangement 54 which may be seen to constitute an improvement over that of Figs. 2 and 3.

The arrangement 54 has a curved outline 56 on its upper or material side. The material 14 in this embodiment is a relatively thin sheet (especially as viewed in Fig. 10) which is curved or bent over part of the base member 16, and secured to the sides 58 thereof, preferably by glueing or by any other suitable means. The pyramidal material of base 16 is such that angled sides are suitable for adhering the sheet material 14 thereto, to provide the aforementioned curved profile.

The arrangement 54 may be secured to the interior of the grille by directly securing the underside 60 of base member 16 thereto, or providing feet on the underside 60, such as feet 42 of Fig. 5.

The dimensions of the prototype of Figs. 9 and 10 are: length 180mm, width 21mm, and height only 6mm. That makes it much easier to locate the arrangement of Figs. 9 and 10 within an accordion, in particular on the inside of the grille, or nearby.

Figs. 11 and 12 show an alternative arrangement 116 for amplifying sound produced by the keyboard and reeds of an accordion. The sound from the keyboard end actually comes from two pickups which are combined together by the circuitry shown in Fig. 14. These pickups are a "'grille pickup" 110 and a "reed block pickup" 112. The grille pickup 110 picks up sound from preferably around 1kHz to 18kHz and the reed block pickup 112 from around 200Hz to 1 kHz. Individually, the sound from each pickup is not particularly satisfactory, but the outputs of the two pickups 110, 112 combine to provide very good reproduction of the instrument's sound. Further, the tone control provided on the circuit board (Fig. 14) operates by sweeping between the two pickups 110, 112, so that the player, using the tone control, can retain his preferred sound when he finds himself playing through different sounding PA systems.

The grille microphone or pickup 110 (Figs. 11 and 12) is in appearance and nature an acoustic 'strip' microphone. It is comprised of two electrets 116, 118, a length 120 of 10mm thick Plastizoat, and a length of ribbed vinyl matting 122 which provides the base and mounting surface. The grille microphone is mounted inside the accordion grille of an accordion (not shown) and runs for as much of the length of the grille as is practical. Sound from the reeds (not shown) enters the Plastizoat and is transmitted into a channel or chamber 124 created by the ribbed vinyl matting. The two electrets 116, 118 are 'facing' into this channel or chamber 124 and thus pick up the sound from the full length of the keyboard. Wiring 126, 128 connects the electrets 116, 118 to a circuit such as the one shown in Fig. 14.

While the arrangement of Figs. 11 and 12 is simple in principle, there are of course many parameters affecting how well it works. Firstly, the channel or chamber 124 is ideally airtight. If it springs a "leak", the result will be "peaky" notes and bad feedback. The thickness of the Plastizoat 120 is important to the frequency response, and is also important to the sound pressure levels at the electrets. If it is too thin, the electrets will distort. The outer surface of the Plastizoat is also a parameter. It has been found to sound best if it is "scuffed" with sandpaper. The volume of the channel or chamber 124 is also important to frequency response. The shape of the channel or chamber 124 is also important. Obviously, if the channel 124 acts as a single pipe, it will have a resonant frequency.

Fig. 12 shows how a channel or chamber 124 is created in such a way that it has a number of different lengths. One way in which the channel 124 may be constructed is to take sheets of ribbed vinyl, cut pieces to the appropriate size, then cut gaps in the "peaks" and fill the "valleys" with wax or some other material so that the channel 124 has the desired shape and volume. The design shown in solid black in Fig. 12 is the preferred shape, but further research could probably achieve even better results. In a production situation, clearly the vinyl or plastic backing containing the channel would be made with the channel (or chamber) 124 ready-moulded into place.

The reed block pickup is a slightly cut down version of the bass pickup shown in Fig. 13. It is glued to a bar attached to the top of the reed blocks and picks up the lower keyboard frequencies by contact. The reason for this approach is that while the grille pickup is excellent at high frequency feedback rejection, it is in fact feedback-prone at lower frequencies. The bar across the reed blocks may be made of any hard material, but rubber is preferred. The reason for this is that the response from each block may be adjusted by the tightness of the mounting screw. A better approach in a production situation may be to use a metal or plastic bar screwed to the reed blocks with a hollow rubber cone used as a washer. The correct amount of contact with each block to give an even response would then be easily adjustable.

There is a side-effect to this means of picking up the lower reed frequencies which some players may like and others may not. When a key is released and a note is expected to stop, the reeds of course do not instantly stop vibrating and this is noticeable with the pickup system of the present invention. In practice, this is not found to be a problem. In fact if it is noticeable at all whilst playing, it simply sounds like a modest amount of room reverberation.

As mentioned earlier, the keyboard tone control operates by sweeping between these two pickups 110, 112. In practice, the way to use this pickup is to be mostly reliant on the grille microphone 110, using just enough of the reed block pickup 112 to "warm" the sound as required.

The bass pickup 114 (Fig. 13) is almost totally a "contact" microphone. An electret 130 is encased in Plastizoat 132 and then both are encased in heat-shrink plastic sheathing 134 so that very little airborne sound can reach the electret 130. As the Plastizoat 132 does have acoustic conduction properties, the outer sheathing 134 is left open-ended to prevent standing waves or resonances occurring within the enclosure. The enclosure is then preferably glued to an appropriate place on the accordion's bass "soundboard", generally quite close to the reed block mountings. This is accomplished by glueing mounting feet 136 to that appropriate place.

The choice of the best possible location for the pickup 114 is very much a matter of trial and error. Even changing the location of the pickup by 5mm can significantly change the resultant sound. The pickup 114 is so sensitive that even the way in which its electrical lead 138 is fixed is of importance. Generally, it is recommended that the pickup 114 be located on the bass soundboard, on the inside of the accordion, with the lead 138 secured to the reed block containing the higher octaves of bass reeds.

This pickup was initially intended to be mounted in the bass chamber alongside the mechanism. The outer sheathing was then perforated with pinholes to give it some high frequency acoustic response. However, clatter from the bass mechanism proved to be an insurmountable problem. Given an instrument with a very quiet mechanism, this approach could be revisited, but on some instruments, mounting the pickup on the inside of the accordion gave the best results. Even so, mechanism clatter can still be audible, and it has been found necessary in the circuitry (Fig. 14) to remove the highest frequencies from the pickup. In practise, the bass pickup picks up reed response from about 10 Hz to 2kHz which does allow enough 'bite' from the bass end. Handling noise/bellows noise can be present, but it has not been found to be excessive or a problem on stage.

Turning now to the circuit of Fig. 14, the grille microphones 110 are energised from the 9V supply by R1 and feed into trimpot RV1 which gives some adjustment between the two electrets. C1 and R2 trim low frequencies from the electrets and the resultant signal appears at one side of the tone control RV2.

The reed block pickup 112 is energised by R6, and C2 and C3 filter out all but a very narrow frequency band. C4 further reduces high frequency response at the first gain stage, and the resultant signal appears at the other side of the tone control RV2. C6, R3 and C7 are quite important to the end sound and are mounted to the copper side of the circuit board on the solder points of the tone pot so that they can be easily changed if required. C7 both reduces circuit hiss and regulates the higher frequencies (abound 1 kHz) of the reed block pickup. C6 and

R3 allow some of the very highest frequencies from the grille microphones 110 to continue to the next stage of the circuit when the tone control is swept towards the reed block pickup 112. The end result is that very high frequencies remain fairly constant, and as the tone control is swept, upper mid range is exchanged for middle/lower middle frequencies.

The now mixed signals reach the volume control RV3 which is situated in mid circuit so that no interaction between the volume controls for keyboard and bass ends is possible. C8 limits any remaining low frequencies. The final gain stage is self explanatory, and the remaining components of the keyboard circuit are R16 and C11 which remove some hiss from the sound. The pickup has ample high frequency and can afford to lose a little at this stage. In the bass circuit, the electret 130 is energised through R17 and R18. C13 is a component which removes a lot of unnecessary low mid frequency from the sound. C14 blocks anything lower than 10 Hz from the first gain stage. The rest of the circuit is fairly self-explanatory with the tone control RV5 being a simple low pass filter, and C18 and C19 being in the circuit to reduce 'mechanism clatter' frequencies.

A good quality battery is desirably used in the circuit of Fig. 14. An inexpensive battery with low capacitance can cause the following effect. The loading of the supply rail by the grille electrets can appear at the output of the final gain stage of the keyboard circuit. An accordion fed back at low frequencies with both volume controls turned down to zero. The cause was a very inexpensive battery, and the problem has never recurred using good quality batteries. Battery life is of the order of 15 to 30 hours of usage.

It can be seen that the present invention provides a microphone arrangement for producing accurately reproduced sounds, using amplification, from musical instruments such as accordions. The base member 16, in a production model, may have upstanding side walls to obviate the use of tape as described in this specification. That base member 16 may be of moulded rubber, plastic or formed from any suitable material.

It is submitted that the pickup system of the present invention is incomparably superior in terms of feedback rejection to any other microphone system presently in use. Further, as a result of this system's properties, it is possible to amplify the lowest octaves of bass reeds to the point where the accordionist can act as the bass player for a group using a totally reed generated sound. The necessity for a "midi" accordion to provide bass playing capability, with its inherent expense, complication and reliability issues is to a large degree eliminated.

The entire contents of the specification and drawings of Australian provisional patent application no. 2002951361 , filed on 10 September 2002. The claims form part of the disclosure of this application.

Claims

1. A microphone arrangement for musical instruments such as accordions, characterised by a closed or sealed chamber in which or in communication with which is microphone means, and by a material, through which sounds from said instrument are adapted to pass to reach said chamber and said microphone.

2. A microphone arrangement according to claim 1 , characterised in that said material is a dense closed cell foam.

3. A microphone arrangement according to claim 2, characterised in that said foam is EVA foam.

4. A microphone arrangement according to any preceding claim, characterised in that said closed chamber is defined by said material and by a base member.

5. A microphone arrangement according to claim 4, characterised in that said chamber may additionally be defined by means adapted to ensure that said chamber is closed.

6. A microphone arrangement according to claim 4 or claim 5, characterised in that said base member has a pyramidal configuration at least on the side which faces said material.

7. A microphone arrangement according to any preceding claim, characterised in that said materially is secured, by glueing, adhering or the like, to said base member.

8. A microphone arrangement according to claim 7, characterised in that said base member is glued or adhered by virtue of the peaks of said pyramidal configuration being glued or adhered to said material.

9. A microphone arrangement according to any preceding claim, characterised in that said microphone means is an electret microphone.

10. A microphone arrangement according to any preceding claim, characterised in that when said instrument is an accordion, said arrangement is located inside the grille of said accordion at the treble end of said accordion.

11. An arrangement for picking up sounds produced by a musical instrument such as an accordion, said arrangement including means through which said sounds may travel, which means is adapted to attenuate said sounds to a predetermined degree, said sounds thereafter reaching a closed chamber in which, or in communication with which, is located microphone means.

12. The invention may further provide, in a broad aspect, a method suitable for amplifying sounds produced by a musical instrument such as an accordion, characterised by the step of:

locating in, or near said instrument a pickup module in which microphone means picks up said sounds from a closed chamber, after they have passed through a medium which may attenuate said sounds to some degree.

13. A microphone or pickup arrangement for picking up sounds from the bass end of musical instruments such as accordions, characterised by microphone means located within a sheath of a first material, and by a second material interposed within said sheath and at least partially surrounding said microphone means, such that said first material and said second material are located between the source of said sounds.

14. A microphone arrangement according to claim 13, characterised in that said first material is in the form of a hollow, open-ended body, and said second material is located within at least part of said body.

15. A microphone arrangement according to claim 14, characterised in that said microphone means is located at or near one end of said body, a portion at or near the other end of said body is hollow, and said other end is open.

16. A microphone arrangement according to claim 14 or claim 15, characterised in that said body is generally cylindrical, said second material occupying the interior of said generally cylindrical portion, and said portion tapers to said other end.

17. A microphone arrangement according to any one of claims 13 to 16, characterised in that said first material is heat-shrink plastic.

18. A microphone arrangement according to any one of claims 13 to 16, characterised in that said first material is a dense closed cell foam material such as EVA.

19. A microphone arrangement according to claim 4 or claim 5, characterised in that said base member has a ribbed configuration at least on the side which faces said material.

20. A microphone arrangement according to claim 19, characterised in that said ribbed configuration is constituted by a series of generally parallel peaks and valleys, each of said peaks and valleys having a generally U-shaped cross-section.

21. A microphone arrangement according to claim 20, characterised in that said chamber is created by filling in some of said valleys and/or removing some of said peaks to produce gaps.