GB2118757A

GB2118757A - Audio transducer

Info

Publication number: GB2118757A
Application number: GB08314227A
Authority: GB
Inventors: Alun David Ashworth-Jones
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-01-21
Filing date: 1983-01-18
Publication date: 1983-11-02
Also published as: GB8314227D0

Abstract

An audio transducer, for a musical instrument, incorporates a sensitive piezo-electric element 5 of composite construction, operating in a simple beam mode. The element responds to sound vibrations in two opposing plates 1, 7 which are separated by rigid supports 8, and between which the element is supported 2, 6 so that it acts under controlled static pressure. This pressure is determined by the fixed spacing of the opposing plates, together with the nature of the material of the fulcrum 6, and the flexibility of the element. These factors are arranged to allow the minimum static pressure on the element consistent with efficient transfer of sound to the element through its own supports. The element is thereby enabled to operate under constantly optimum conditions, despite the extremes of pressure to which the device as a whole may be subjected in its normal position beneath the saddle of a stringed instrument. The result is the production of a high-level audio signal. <IMAGE>

Description

SPECIFICATION Controlled pressure audio transducer The idea of using the piezo-electric effect to provide an audio signal from vibrations present in the bridge of a stringed musical instrument is well known. Normally this is achieved by embedding one or more piezo-electric crystals in various materials acted on directly by the strings as they pass over the bridge.

The controlled pressure transducer, as here described, employs a more sensitive flexible element of composite construction, typically a ceramic bimorph, operating in a situation free from the influence of external mechanical pressure so that the efficiency of the element, and its sensitivity to sound vibrations, can be maximised.

These conditions can be arranged in the following manner: With reference to Fig. 1, showing a side view, two rectangular plates of rigid material, 1 and 7, such as hardwood or GRP board, are held in a position parailel to each other, and a short distance apart, by rigid supports at each end, 8. These may be of the same material as the plates. Within the box section thus formed, a bimorph element, 5, is attached to one plate, designated the upper one, by a small piece of adhesive material at each end, 2. This adhesive is chosen to be a good conductor of sound yet preferably possess some flexibility, and holds the element just clear of and parallel to the plate as shown.

The element operates in a simple beam mode, and the fulcrum, 6, which links it to the base plate, 7, consists of a cylindrical piece of soft plastic material, of a type which wi[l conduct sound efficiently whilst maintaining the minimum pressure on the element necessary for reliable contact and transfer of sound. Vibrations induced in the upper plate, 1, which is necessarily under considerable and often varying pressure from the bridge or bridge saddle resting on it, are thus transferred to the bimorph element which is subjected to a constant minimal pressure from the fulcrum.

The base plate rests upon the surface of the instrument, which carries sound vibrations of lesser magnitude than the bridge saddle, and partially altered phase. This confers a counteracting dynamic pressure on the element by way of the fulcrum. As the element is largely free of static pressure, its efficiency is enhanced as already mentioned, and the resulting high level audio output is taken by way of soldered connections, 4, and audio cable, 3.

Fig. 2 shows a cross-sectional view with an alternative base plate arrangement offering a more robust structure. The base plate, 7, forms the bottom of a channel, the sides of which enclose the element, and almost meet the top face, leaving room for a rubber gasket, 9, to seal the device, with only slight loss of performance through damping of the upper plate.

Claims (filed on 18.1.83) 1. An audio transducer, for use with musical instruments, having a rigid framework or enclosure which may be interposed between two vibrating surfaces, or one vibrating surface and one static surface enabling a piezo-electric element within to respond to the difference in vibrations between the two surfaces in conditions largely independent of the mechanical pressure between the two surfaces.

2. A transducer as in claim 1 incorporating one or more pieze-electric elements of composite construction operating in simple beam mode.

3. A transducer as in claim 2 substantially as described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Controlled pressure audio transducer The idea of using the piezo-electric effect to provide an audio signal from vibrations present in the bridge of a stringed musical instrument is well known. Normally this is achieved by embedding one or more piezo-electric crystals in various materials acted on directly by the strings as they pass over the bridge. The controlled pressure transducer, as here described, employs a more sensitive flexible element of composite construction, typically a ceramic bimorph, operating in a situation free from the influence of external mechanical pressure so that the efficiency of the element, and its sensitivity to sound vibrations, can be maximised. These conditions can be arranged in the following manner: With reference to Fig. 1, showing a side view, two rectangular plates of rigid material, 1 and 7, such as hardwood or GRP board, are held in a position parailel to each other, and a short distance apart, by rigid supports at each end, 8. These may be of the same material as the plates. Within the box section thus formed, a bimorph element, 5, is attached to one plate, designated the upper one, by a small piece of adhesive material at each end, 2. This adhesive is chosen to be a good conductor of sound yet preferably possess some flexibility, and holds the element just clear of and parallel to the plate as shown. The element operates in a simple beam mode, and the fulcrum, 6, which links it to the base plate, 7, consists of a cylindrical piece of soft plastic material, of a type which wi[l conduct sound efficiently whilst maintaining the minimum pressure on the element necessary for reliable contact and transfer of sound. Vibrations induced in the upper plate, 1, which is necessarily under considerable and often varying pressure from the bridge or bridge saddle resting on it, are thus transferred to the bimorph element which is subjected to a constant minimal pressure from the fulcrum. The base plate rests upon the surface of the instrument, which carries sound vibrations of lesser magnitude than the bridge saddle, and partially altered phase. This confers a counteracting dynamic pressure on the element by way of the fulcrum. As the element is largely free of static pressure, its efficiency is enhanced as already mentioned, and the resulting high level audio output is taken by way of soldered connections, 4, and audio cable, 3. Fig. 2 shows a cross-sectional view with an alternative base plate arrangement offering a more robust structure. The base plate, 7, forms the bottom of a channel, the sides of which enclose the element, and almost meet the top face, leaving room for a rubber gasket, 9, to seal the device, with only slight loss of performance through damping of the upper plate. Claims (filed on 18.1.83)

1. An audio transducer, for use with musical instruments, having a rigid framework or enclosure which may be interposed between two vibrating surfaces, or one vibrating surface and one static surface enabling a piezo-electric element within to respond to the difference in vibrations between the two surfaces in conditions largely independent of the mechanical pressure between the two surfaces.