CN1351813A

CN1351813A - Bending wave acoustic device

Info

Publication number: CN1351813A
Application number: CN00808007A
Authority: CN
Inventors: 克里斯蒂恩·埃利斯
Original assignee: New Transducers Ltd
Current assignee: NVF Tech Ltd
Priority date: 1999-07-02
Filing date: 2000-06-30
Publication date: 2002-05-29
Also published as: AU5547500A; JP2003503990A; GB9915361D0; TW488183B; HK1041400A1; WO2001003467A2; NZ515327A; EP1192839A2; WO2001003467A3

Abstract

An acoustic device has a panel (11) capable of supporting resonant bending wave modes and transducers (19) mounted on the panel. Sometimes, the acoustic response of panel and transducers may have a whole-body resonance peak at a particular frequency. To control this, a mass (21) may be added to the panel, for example on a compliant coupling (23).

Description

Audio unit

Technical field

What the present invention relates to is audio unit, particularly relates to the audio unit that uses profile resonance bending wave pattern in the plate.

Background technology

Among the WO 97/09842 distributed mode loudspeaker has been described.The bending wave transducer excitation goes out to be distributed in the resonance mode on the plate, and produces sound by this.

But this loud speaker can be subjected to the adverse effect from one-piece pattern.These one-piece patterns are low-frequency vibrations that plate produces during as a mass motion.When plate is placed in one shallowly when enclosing in the chamber, a kind of situation of this kind pattern promptly may take place.If it is motionless that the external margin of plate is fixed, so, the middle part of plate can porpoise.Vibration frequency can be subjected to being enclosed the influence of the air cushion that the chamber surrounds, and occurs in the frequency place of about 1000Hz.This generation for sound is quite important.Another example of one-piece pattern is the vibration mode that is associated with the plate that vibrates at the outstanding place of holding of elasticity.

The discrete resonance meeting that is produced by one-piece pattern causes peak value in frequency response.This is very disadvantageous, thus distributed mode device half relate to becoming outside the frequency range of one-piece pattern and work.But it is not always feasible doing like this, therefore, needs to reduce the influence of this pattern to the distribution pattern audio unit.

Summary of the invention

According to invention, a kind of audio unit is provided, comprising:

A plate can be supported bending wave, and at whole resonance frequency place whole resonance can take place;

A transducer can motivate distribution bending wave pattern and plate is sounded in plate; And

A mass, the fixing position that separates with transducer onboard, the resonance that control is whole.

This mass is preferably fixing onboard by a kind of coupler, and this coupler can remove the coupling of mass and plate when high frequency.This coupler can be a kind of coupler of being obedient to, and such as spring or be obedient to sheet metal, can remove the coupling of mass and resonance bending wave in frequency during much larger than whole resonance frequency basically.This biddability also can be obtained from the top layer of plate and the elasticity of core body.As other a kind of scheme or as a supplement, be obedient to binding agent and also can form the coupler of being obedient to that mass is fixed in plate.When frequency when being positioned at the resonance frequency of being obedient to the mass on the coupler, mass decoupling on the slave plate basically.When the biddability of coupling body is obedient in selection, is positioned at the resonance frequency of being obedient to the mass on the coupling body and will be suitable for desired sound result, the resonance frequency of mass-be obedient to coupler can be higher than the one-piece pattern frequency.

The fundamental frequency of bending wave pattern is provided by following formula under isotropic situation:

A is the plate area herein, and B is a bending stiffness, and reaching μ is area density, Kg/m ²Be provided with fundamental frequency suitably lower in the profile pattern loud speaker formerly, this model will have the pattern of abundant distribution in operating frequency range.Yet, in some application scenario, also may occur, plate need be also harder than the rigidity of the best, that is to say that plate needs " really up to the mark ", and its bending stiffness value B is greater than for reducing the fundamental frequency rigidity of selection usually.In this case, the influence of minimizing one-piece pattern is particularly useful.

The mass that is fixed to plate can be directly proportional with the plate moving-mass, promptly be about the effective exercise quality percent 10 or percent 20 to percent 200 or percent 300 of effective exercise quality.For example, the effective exercise plate quality of light multimedia speaker is 8 grams.In this case, need the mass of 1 to 10 gram is fixing onboard.But the mass value must become according to a plurality of parameters, such as the quality of system, relevant coefficient of elasticity and the whole mechanical connection of assembly reality.

Mass preferably is fixed in the entad of plate.This selection and mode activated are irrelevant, but have considered and mass has been arranged on from the nearer position of the barycenter of plate, make the mass of interpolation can control one-piece pattern.Preferred positions can be a such position: the coupling of this position and Hyporesonance pattern and the coupling of one-piece pattern want much weak.By system test or to the Computer Analysis of plate mechanical connection, can find this position.

Can be provided with one and enclose the chamber behind plate, this encloses the chamber can be open or sealing, and especially enclosing the chamber for simplicity can be more shallow.Enclose the chamber and can be used as sound insulating member.

The invention still further relates to a kind of method of making audio unit, step is as follows: the plate that can support bending wave is provided, a transducer is set on this plate, use this transducer activation profile in plate to resonate the bending wave pattern and plate is sounded, determine the frequency response of plate, find out the integral body resonance at whole resonance frequency place, a mass is added in the whole resonance of ad-hoc location control.

By network analysis or mathematical computations, can determine the frequency response of plate.In case made an audio unit, just can duplicate audio unit simply, and needn't when making each unit, all will determine whole resonance frequency by similar transducer and the mass of using similar plate, install onboard in a similar manner.

Use one to be obedient to coupler and can to finish with the fixing step onboard of mass.

Description of drawings

Below, with reference to accompanying drawing a specific embodiment of the present invention is described by way of example purely.Wherein,

Fig. 1 illustrates the end view according to a loud speaker of invention;

Fig. 2 illustrates the schematic diagram according to a loud speaker of invention;

Fig. 3 is illustrated in the frequency response of loud speaker when not adding mass;

Fig. 4 illustrates the frequency response of loud speaker when adding mass.

Embodiment

A plate 11 is installed on a framework 13, and the thickness of this plate 11 is 0.35 millimeter, and length is 206.5 millimeters, and width is 147 millimeters, and mechanical impedance is 6.22 Newton meters, and fundamental frequency is that 203 hertz and coincidence frequency (coincidence frequency) are 7.8 hertz.Framework 13 has a back structures, defined and impaled a volume and be 0.6 liter the chamber of enclosing.

The best plate thickness of same material is 0.35 millimeter, and mechanical impedance is 6.22 Newton meters, and is long 333 millimeters, wide 284 millimeters, and fundamental frequency is that 78 hertz and coincidence frequency are 7.8 kilo hertzs.Fundamental frequency according to plate of the present invention is 203 hertz, and is more much higher than 78 hertz.

Plate 11 is by being bonded in the double-sided foam tape 17 of 4 millimeters thick on plate 11 peripheries, and elastic bearing is on framework 13, and the supporting that formation is obedient to.If useful, other edge bearing can be set, for example clamp the supporting of supporting, simple support.

As shown in Figure 2, on according to the favourable position of being taught as of WO 97/09842, two exciters 9 have been installed.These two exciters are 25 millimeters exciters, series wiring, and the direct current group is 9 ohm of resistances.Also can adopt and be connected in parallel.

Fig. 3 is illustrated in the sound-pressure-level measurement result as frequency function who records apart from 1 meter of plate.A tangible peak value that occurs at the 500-1KHz place has been considered to show the one-piece pattern effect that vibration causes on the air cushion that plate 11 enclosing in the chamber 15.This one-piece pattern is subjected to enclosing the control of the biddability of air in the chamber.

Then, with a mass 21, promptly little counterweight adds onboard along the side directions 88mm of plate and apart from the side 63mm place of plate.This mass is obedient to plastics with a slice two sides band glue that is similar to traditional adhesive tape thin and is fixed.Mass is 3.1 grams.

As can be seen from Figure 4, spike is controlled basically, and at high frequency treatment significant the variation is not taken place.

The present invention is that mass 21 is controlled output selectively, reduces sensitiveness fully, makes resonance frequency be significantly less than the one-piece pattern frequency.At high frequency treatment, along with plate becomes the more mode of crypto set, mass 21 gradually with plate 11 decouplings.

The position of mass obviously is very important for this control of fine setting.Can adjusting position, quality and mass installed onboard biddability, come the response of control system, for example so that the more uniform voice response as frequency function to be provided.

Claims

1. audio unit comprises:

A mass is fixed onboard, and like this, mass can be controlled whole resonance.

2. audio unit as claimed in claim 1 is characterized in that, this mass is fixing onboard by a coupler, and this coupler can remove the coupling of mass and plate when high frequency.

3. audio unit as claimed in claim 2 is characterized in that, this coupler is a kind of coupler of being obedient to, and can remove the coupling of mass and resonance bending wave in frequency during much larger than whole resonance frequency basically.

4. the described audio unit of arbitrary as described above claim is characterized in that, when not having described mass, the frequency response of plate has a peak value at the overall frequency place, and this peak value is fixed with in the audio unit of described mass onboard, is fallen by smooth substantially.

5. the described audio unit of arbitrary as described above claim is characterized in that, this mass be plate the effective exercise quality percent 10 to percent 300 between.

6. the described audio unit of arbitrary as described above claim is characterized in that, this mass is positioned at the position of the barycenter of close plate on the plate.

7. the described audio unit of arbitrary as described above claim is characterized in that, also is included in and defines a back structures of enclosing the chamber behind the backboard.

8. the described audio unit of arbitrary as described above claim is characterized in that, also comprises a sound insulating member around the plate edge.

9. method of making audio unit, step is as follows:

The plate that can support bending wave is provided, a transducer is set on this plate,

Use this transducer activation profile in plate to resonate the bending wave pattern and plate is sounded,

Determine the frequency response of plate,

Find out the integral body resonance at whole resonance frequency place,

A mass is added in an ad-hoc location to control whole resonance.

10. method as claimed in claim 9 also comprises step: by basically the described plate that has mass and the transducer that applies being duplicated, to make other audio unit.

11. as claim 9 or 10 described methods, wherein, the fixed mass body utilizes one to be obedient to coupler and to reach in the step of plate.

12. as each described method of claim 9 to 11, wherein, when not having described mass, the frequency response of plate has a peak value at the overall frequency place, this peak value is fixed with in the audio unit of described mass onboard, is fallen by smooth substantially.