Noise cancellation apparatus - Patent Review 5673325

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BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a noise cancellation apparatus and, more particularly, to an apparatus for canceling or reducing background acoustic noise for use with a telephone handset or a boom microphone device or boom headset or the like.

2. Description of the Prior Art

As is to be appreciated, in numerous situations, the presence of background acoustic noise is undesirable. As an example, consider the situation in which an operator is attempting to conduct a telephone conversation from a telephone or such similar device located in a noisy area. In this situation, loud acoustic background noise is received by a microphone in the handset of the telephone and converted to an electrical signal which is supplied to the telephone(s) of the person(s) having the conversation with the operator and is converted thereat to an acoustic signal. As a result, the person to whom the operator is communicating constantly hears the loud background noise. Further, when the person is speaking, such speech is combined with the background noise and, as such, may be difficult for the other person(s) to understand. As a result, the operator may have to shout into the microphone of the telephone. Furthermore, the signal representing the background noise is also supplied from the microphone in the operator's handset to the speaker in the operator's handset. Thus, the operator also constantly hears the background noise from the speaker in the operator's handset and, when the other person is speaking, may impair the understanding thereof.

As another example, consider the situation in which a pilot who is operating a helicopter or the like wishes to communicate with another person by way of radio frequency (RF) communication. In this situation, the pilot typically speaks into a so-called boom microphone or boom headset which is coupled to a radio transmitting/receiving device whereupon the speech is converted into RF signals which are transmitted to a second receiving/transmitting device and converted therein to speech so as to be heard by the other person(s). As with the above situation of a telephone located in a noisy area, the loud background noise from the helicopter is received and converted into an electrical signal by the boom microphone or headset device and thereafter supplied to the receiving device. As a result, the person(s) communicating with the pilot hears the loud background noise. This may be particularly annoying when the pilot leaves the radio transmitting/receiving device in the "ON" position while operating the helicopter.

As yet another example, consider voice verification and/or recognition systems into which an operator must speak for access, for instance to a physical facility or, to operate a computer or automatic teller machine. Background noise can prevent access (no recognition or verification due to background noise) or can provide false access by false verification.

In an attempt to reduce background noise so as to improve performance of a telephone or a boom microphone or headset or the like located in a noisy environment or the like, pressure gradient microphones may be utilized. Basically, a pressure gradient microphone responds to the difference in pressure at two closely spaced points. When used in an environment where the pressure gradient of the background noise is isotropic, the electrical signal produced by the pressure-gradient microphone due to such background noise is effectively zero. However, in most actual situations, the pressure gradient of the background noise is not isotropic and, as a result, in these situations, the performance of the pressure-gradient microphone is adversely affected. Additionally, since voice or speech propagates in more than one direction, the electrical signal produced by the microphone which corresponds thereto is often degraded. Thus, even if a pressure gradient microphone is utilized in either a telephone handset or a boom microphone, the desired amount of background noise cancellation may not be sufficient and the performance may not be adequate.

Furthermore, since two opposite sides of a pressure-gradient microphone respond to acoustic pressure, as previously mentioned, the handset of an existing telephone would have to be substantially modified so as to enable these two sides of the microphone to respond to the acoustic pressure. Moreover, as a result of using such a microphone in a telephone handset, the electrical signals produced therefrom should be amplified. Thus, to replace the conventional microphone in a telephone handset of an existing telephone with a pressure-gradient microphone would typically necessitate replacing the handset with a new handset and, as such, would be relatively expensive.

As an alternative to using pressure-gradient microphones, an acoustic feed-back type system may be utilized. Such a system normally includes compensation filters which are used to equalize the transfer function of the speakers. Since the characteristics of the speakers are tightly controlled by these filters, the cost of the filters is relatively high. As a result, such acoustic feed-back systems are typically relatively expensive.

Thus, the prior art has failed to provide a relatively low-cost means for reducing background noise to an acceptable level for use with telephones and/or boom microphone devices or the like, and a cost-effective means for enabling existing telephones to reduce background noise to an acceptable level.

OBJECTS AND SUMMARY OF THE INVENTION

An object of the present invention is to provide noise reduction apparatus which overcomes the problems associated with the prior art.

More specifically, it is an object of the present invention to provide noise reduction apparatus which reduces background noise to an acceptable level.

Another object of the present invention is to provide noise reduction apparatus as aforementioned for use with a telephone or boom microphone or headset device or to provide a noise reduction microphone device or the like.

It is still another object of the present invention to provide noise reduction apparatus as aforementioned which is relatively inexpensive.

It is yet another object of the present invention to provide a relatively low-cost noise reduction apparatus for use with telephones which is operable with standard available on-line power.

A still further object of the present invention is to provide a relatively low-cost noise reduction apparatus which is readily adaptable to handsets of existing telephones and which is operable with standard available on-line power.

A yet further object of the present invention is to provide a relatively low-cost noise reduction apparatus for use with telephones or which may be readily adaptable to handsets of existing telephones which enables an operator to selectively amplify a received signal or, which may be used in a boom microphone or headset or, which may be used as a noise canceling microphone.

In accordance with an aspect of this invention, a telephone handset apparatus for use with a telephone operable by standard power supplied to the telephone handset for transmitting and receiving signals representing speech between two or more operators is provided. The apparatus includes a housing having a first microphone means for receiving a first acoustic signal composed of speech from the operator using the apparatus and background noise in the vicinity of the speech and for converting the first acoustic sound to a first signal, and a second microphone means arranged at a predetermined angle with respect to the first microphone means for receiving a second acoustic sound composed of substantially the background noise and for converting the second acoustic sound to a second signal; and a device for subtracting the second signal from the first signal so as to obtain a signal representing substantially the speech.

In another aspect the invention provides a boom microphone or headset device for transmitting and receiving signals representing speech by at least one, preferably two or more operators. The device includes housing having a first microphone means for receiving a first acoustic signal composed of speech from the operator using the device and background noise in the vicinity of the speech and for converting the first acoustic sound to a first signal and a second microphone means arranged at a predetermined angle and/or distance with respect to the first microphone means for receiving a second acoustic signal composed substantially of background noise and for converting the second acoustic sound to a second signal; and an apparatus for subtracting the second signal from the first signal so as to obtain a signal representing substantially speech.

The boom microphone or headset can be used in flight (e.g., helicopter or airplane) or in other settings such as telephones, or voice recognition and/or verification systems for instance, for access to a physical facility or to a computer (either via direct or indirect interface or via telephone lines) or to an automatic teller machine or, in other recognition and/or verification systems. The first and second microphones arranged at a predetermined angle and/or distance with subtraction apparatus disclosed herein can also be used in the area of ambient noise cancellation for microphones in acoustic surveillance or telemetry or even directional microphones such as directional microphones with sidelobes.

Other objects, features and advantages according to the present invention will become apparent from the following detailed description of the illustrated embodiments when read in conjunction with the accompanying drawings in which corresponding components are identified by the same reference numerals.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a telephone having a noise reduction apparatus according to an embodiment of the present invention;

FIG. 2 is a block diagram of the noise reduction apparatus used in the telephone of FIG. 1;

FIG. 3A is a front plan view of the receiver portion of the telephone of FIG. 1;

FIG. 3B is a side elevational view of the receiver portion of the telephone of FIG. 1 with the top removed;

FIG. 4 is a schematic diagram of the block diagram of FIG. 2;

FIG. 5 is another schematic diagram of the noise reduction apparatus illustrated in FIG. 2; and

FIG. 6 illustrates a boom microphone device utilizing a noise reduction apparatus according to an embodiment of the present invention;

FIG. 7 is schematic diagrams to which reference will be made in explaining the operation of the present invention;

FIG. 8 illustrates of a noise reduction apparatus according to the present invention;

FIG. 9 illustrates boom microphone and headset embodiments of the invention (FIGS. 9A and 9B each showing an embodiment having particular placement of the microphone; FIG. 9C showing an overview of the headset and FIGS. 9D and 9E showing side views of the boom microphone);

FIG. 10 is schematic diagrams of the noise reduction apparatus of FIG. 8;

FIG. 11 illustrates a phase reversing circuit;

FIG. 12 illustrates an oppositely charged microphone circuit