GB1561895A

GB1561895A - Motor vehicle audio apparatus

Info

Publication number: GB1561895A
Application number: GB4267776A
Authority: GB
Original assignee: ORLIK H
Current assignee: ORLIK H
Priority date: 1975-10-28
Filing date: 1976-10-14
Publication date: 1980-03-05
Also published as: IT1071524B; FR2394420B1; ES452722A1; FR2394420A1; DE2646232A1

Description

(54) MOTOR VEHICLE AUDIO APPARATUS (71) I, HENRI ORLIK, a French Citizen, of 117 Rue de Montreuil, 75011 Paris, France, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following state ment : -.

This invention concerns audio equipment, such as radios, casette players, cartridge players and the like, of the kind adapted for mounting in a motor vehicle. For convenience, such equipment will be referred to herein as "car audio apparatus".

With car audio apparatus it is often necessary to effect frequent correction of the sound level delivered by loudspeakers of the apparatus because of successive variations in effective internal sound level generated by both changes in engine speed and speed of movement of the vehicle, as well as by changes in the level of externally generated noise, which, of course tends to vary conbinuously The need to make frequent manual correction, by adjustment of an appropriate potentiometer or rheostat distracts the attention of the driver and is both dangerous and a nuisance.It is therefore an aim of the present invention to provide apparatus in which this adjustment is effected automatically, so as continuously to adapt the sound level delivered by the loudspeakers of the apparatus as a function of the level of sound in the interior of the vehicle other than that produced by the loudspeakers themselves.

According to the present invention there is provided motor vehicle audio apparatus comprising at least one loudspeaker, an acousto-electric transducer operative to provide a control signal of a magnitude dependent on the level of sound within the vehicle, a low-pass filter operative to remove components of said control signal having frequencies greater than the lowest frequency produced by the loudspeaker, and means for automatically varying the sound volume emitted by the or each loudspeaker according to the magnitude of the filtered control signal.

The acousto-electric transducer is preferably a piezo-electric sensor whilst the low-pass filter may pass only frequencies of the order of 100 Hz and below. An amplifier may be provided preferably with a gain of about 1000 for amplifying the filtered signal from the transducer. An integrator may be provided for intergrating the amplified and filtered signal, the output of the integrator being used to control variable gain at a first pre-amplification stage of the audio equipment.

It will be understood that the control signal will have a magnitude which is substantially independent of the sound volume issuing from the loudspeaker(s) since the frequencies of the components of that sound are greater than the cut-off frequency of the low-pass filter. There is thus no likelihood of a "runaway" feedback situation in which increased loudspeaker volume is detected to produce further increased volume and so on.

The invention will be described further, by way of example, with reference to the accompanying drawing, in which: - Fig. 1 is a block diagram illustrating a preferred embod!iment of the invention; Fig. 2 is a block diagram illustrating a modification of the arrangement of Fig. 1: Fig. 3 is a detailed circuit diagram illustrating a low-pass filter, integrator and amplifier of apparatus in accordance with the invention and designed to provide a compensatory variation of sound level of about 6 decibels on a transistor receiver of 500 milliwatts output power.

The apparatus of Fig. 1 comprises a piezoelectric sensor 1, positioned on a structural element 2 in a passenger compartment of a vehicle and connected to a low-pass filter 3, followed by an amplifier 4 which supplies a signal to an integrator 5. The voltage output of integrator 5 (which voltage varies according to the noise level sensed by the sensor 1) is applied to a pre-amplifier 6 to control the sound level of one or more loudspeakers 7 of the audio apparatus.

In the apparatus of Fig. 2 the piezo-electric sensor 1 is connected to a potentiometer 8 and the output of potentiometer 8 is con nected to an appropriate integrated circuit device 9 such as that known under the designation "Operational Integrated Circuit SN76020" and available from the Company known as "Texas Instruments" connected to combine the functions of low-pass filter and amplifier of gain 1000. The output of the integrated circuit 9 is connected, by way of an integrator, to a simple transistor 10 of the "field effect" type, connected as a variable resistance for the control of the audio frequency level. The integrated signal may alternatively be connected to the automatic volume control (A.V.C.S of the audio equipment, which may be a radio.

It is fitting to point out that the device can be adapted equally well to mono equlip- ment as to stereo or even quadraphonic equipment.

Fig. 3 illustrates a circuit comprising low pass filter, amplifier and integrator using discrete components, the resistors having, as examples, the following values.

R1 -560 kilo-ohms R2 -560 kilo-ohms R3 - 16 kilo-ohms R4 - 5 kilo-ohms R5 -1-2 kilo-ohms R6 - 1 kilo-ohms R7 - 33 kilo-ohms R8 - 6-9 kilo-ohms R9 - 5 kilo-ohms R10- 10 kilo-ohms R1 1-690 ohms Rl2- 10 kilo-ohms R13- 10 kilo-ohms whilst the capacitances or condensers as illustrated will have the following capacities, voltage ratings being shown in parenthesis.

Cl- 50 microfarads (16 volts) C2- 10 nanofarads C3- 50 microfarads (6 volts) C4- 50 microfarads (6 volts) C5-250 microfarads (6 volts) C6- 50 microfarads (6 volts) C7- 10 microfarads (12 volts) The circuit further includes three transistors, T1, T2 and T3, which may, for example, be those designated respectively "BC 107", "BC 177", and "2N 1990" in the catalogue of the Company known as "Radiotechnique", and a diode D1 which may be that designated "1N 914" in the said catalogue.

Interconnection of these components, in accordance with the diagram of Fig. 3, can be very economically realised, by so-called printed circuit techniques.

Because of this possibility of very compact and very economical implementation, -it has now become practicable to produce such devices for automatic correction of the sound level delivered by the loudspeakers of car audio equipment at an economical price.

Finally, it will be understood that the invention is in no way limited to the illustrated examples described above; on the conrary, the invention extends to all the variants of execution or application which are equivalent or comparable, for instance by inversion Of transposition of the dispositions described or shown.

In this respect it is to be mentioned that although in the diagram of Fig. 3 the letter E has been used to indicate "input" and the letter S has been used for "output" and the signs + and - have been used for the electric supply, one will not depart from the scope of the invention by substituting batteries in the place of the electric supply of the vehicle, nor by changing the working voltage of the various elements.

By way of a variant which is within the scope of the invention, mention is made of the possibility of combining the potentiometer 8 (Fig. 2) with an existing volume regulator potentiometer of a car radio receiver, so that their respective gains act inversely, under the control of a control button. Thus the sound volume control potentiometer may be mechanically connected (for example, coaxially) to the potentiometer 8 such that actuation of the volume control potentiometer also actuates the potentiometer 8 receiving the transducer output, the potentiometers being arranged in inverse relationship such that as an electrical output of one is caused to increase by mechanical actuation an electrical output of the other is caused to decrease and vice versa.

WHAT I CLAIM IS: 1. Motor vehicle audio apparatus comprising at least lone loudspeaker, an acousto-electric transducer operative to provide a control signal of a magnitude dependent on the level of sound within the vehicle, a low-pass filter operative to remove components of said control signal having frequencies greater than the lowest frequency produced by the loudspeaker, and means for automatically varying the sound according to the magnitude of the filtered control signal.

2. Apparatus as claimed in claim 1 in which the low-pass filter is operative to pass frequencies below approximately 100 Hz.

3. Apparatus as claimed in claim 1 or 2 in which the acousto-electric transducer is a piezo-electric sensor.

4. Apparatus as claimed in any preceding claim in which the means for automatically varying the sound volume of the or each loudspeaker comprises an amplifier

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. nected to an appropriate integrated circuit device 9 such as that known under the designation "Operational Integrated Circuit SN76020" and available from the Company known as "Texas Instruments" connected to combine the functions of low-pass filter and amplifier of gain 1000. The output of the integrated circuit 9 is connected, by way of an integrator, to a simple transistor 10 of the "field effect" type, connected as a variable resistance for the control of the audio frequency level. The integrated signal may alternatively be connected to the automatic volume control (A.V.C.S of the audio equipment, which may be a radio. It is fitting to point out that the device can be adapted equally well to mono equlip- ment as to stereo or even quadraphonic equipment. Fig. 3 illustrates a circuit comprising low pass filter, amplifier and integrator using discrete components, the resistors having, as examples, the following values. R1 -560 kilo-ohms R2 -560 kilo-ohms R3 - 16 kilo-ohms R4 - 5 kilo-ohms R5 -1-2 kilo-ohms R6 - 1 kilo-ohms R7 - 33 kilo-ohms R8 - 6-9 kilo-ohms R9 - 5 kilo-ohms R10- 10 kilo-ohms R1 1-690 ohms Rl2- 10 kilo-ohms R13- 10 kilo-ohms whilst the capacitances or condensers as illustrated will have the following capacities, voltage ratings being shown in parenthesis. Cl- 50 microfarads (16 volts) C2- 10 nanofarads C3- 50 microfarads (6 volts) C4- 50 microfarads (6 volts) C5-250 microfarads (6 volts) C6- 50 microfarads (6 volts) C7- 10 microfarads (12 volts) The circuit further includes three transistors, T1, T2 and T3, which may, for example, be those designated respectively "BC 107", "BC 177", and "2N 1990" in the catalogue of the Company known as "Radiotechnique", and a diode D1 which may be that designated "1N 914" in the said catalogue. Interconnection of these components, in accordance with the diagram of Fig. 3, can be very economically realised, by so-called printed circuit techniques. Because of this possibility of very compact and very economical implementation, -it has now become practicable to produce such devices for automatic correction of the sound level delivered by the loudspeakers of car audio equipment at an economical price. Finally, it will be understood that the invention is in no way limited to the illustrated examples described above; on the conrary, the invention extends to all the variants of execution or application which are equivalent or comparable, for instance by inversion Of transposition of the dispositions described or shown. In this respect it is to be mentioned that although in the diagram of Fig. 3 the letter E has been used to indicate "input" and the letter S has been used for "output" and the signs + and - have been used for the electric supply, one will not depart from the scope of the invention by substituting batteries in the place of the electric supply of the vehicle, nor by changing the working voltage of the various elements. By way of a variant which is within the scope of the invention, mention is made of the possibility of combining the potentiometer 8 (Fig. 2) with an existing volume regulator potentiometer of a car radio receiver, so that their respective gains act inversely, under the control of a control button. Thus the sound volume control potentiometer may be mechanically connected (for example, coaxially) to the potentiometer 8 such that actuation of the volume control potentiometer also actuates the potentiometer 8 receiving the transducer output, the potentiometers being arranged in inverse relationship such that as an electrical output of one is caused to increase by mechanical actuation an electrical output of the other is caused to decrease and vice versa. WHAT I CLAIM IS:

1. Motor vehicle audio apparatus comprising at least lone loudspeaker, an acousto-electric transducer operative to provide a control signal of a magnitude dependent on the level of sound within the vehicle, a low-pass filter operative to remove components of said control signal having frequencies greater than the lowest frequency produced by the loudspeaker, and means for automatically varying the sound according to the magnitude of the filtered control signal.

for amplifying the control signal from the transducer, an integrator for integrating the amplified control signal, and a preamplifier operative to control the sound level of the or each loudspeaker in accordance with the magnitude of the integrated control signal.

5. Apparatus as claimed in any preceding claim further comprising a potentiometer to which the output of the acoustoelectric transducer is applied, the control signal being tapped from the potentiometer.

6. Apparatus as claimed in claim 5 further comprising a sound volume control potentiometer mechanically connected to the potentiometer to which the output of the acoustbelectric transducer is applied, such that actuation of the volume control potentiometer also actuates the potentiometer receiving the transducer output, the potentiometers being arranged in inverse relationship such that as an electrical output of one is caused to increase by mechanical actuation an electrical output of the other is caused to decrease and vice versa.

7. Motor vehicle audio apparatus substantially as hereinbefore described with reference to and as illustrated in Fig. 1, Fig.

2 or Fig. 3 of the accompanying drawings.