HK1084284A - Noise reduction headset - Google Patents

Description

Noise-reducing headphone

Technical Field

The present invention relates to noise reducing headsets (headsets), and more particularly, to noise reducing headsets having active noise reduction circuitry and talk-through circuitry.

Background

U.S. Pat. Nos. 6,347,146, 6,597,792, and 6,831,984 disclose relevant prior art.

Disclosure of Invention

In one aspect of the present invention, a noise reducing headphone includes: an active noise reduction circuit for providing active noise reduction; a telephony circuit for providing telephony capabilities; and a switching element for disabling one or both of the noise reduction circuit and the call circuit.

In another aspect of the present invention, a noise reducing headphone includes: a first signal path including active noise reduction and telephony; a second signal path including telephony without active noise reduction; a selection circuit constructed and arranged to select either the first signal path or the second signal path.

In another aspect of the present invention, a noise reducing headphone includes: an active noise reduction signal path; and a speech signal path including a microphone and a frequency selective filter for filtering input from the microphone, the filter constructed and arranged to substantially attenuate frequencies not in the speech band.

In another aspect of the invention, a method of operating a noise reducing headset including an active noise reducing signal path and a talk signal path, the method comprising: providing power to an active noise reduction control signal path and a talk signal path; the noise reduction control signal path is disabled if power to the path of the active noise reduction control signal is below a first threshold level.

Drawings

Fig. 1, 2 and 3 are block diagrams.

Fig. 4A, 4B, 4C, 4D, and 4E are portions of a schematic circuit diagram.

Detailed Description

Referring to fig. 1, a block diagram of an active noise reducing headset with "talk" capability is illustrated. Active Noise Reduction (ANR) headphones are discussed in us patent 4,456,675. ANR headphones typically include earmuffs (earcups) that fit within (inner-auricles), over (supra-auricles), or around the ear. The earmuffs provide passive attenuation of ambient noise. In addition, ANR headphones include electronics that significantly attenuate unwanted noise, for example, by radiating acoustic energy that cancels out ambient noise. ANR headphones typically include electronic circuitry that is capable of electronic communication with a user of the ANR headphone. In some cases, a user of the ANR headset may wish to hear some sound communication in the surrounding environment. For example, a wearer of an ANR headset suitable for military applications may wish to hear not only electronic communications but also voice communications from people in the vicinity. In this situation, it may be desirable to have a "talk" capability, which typically includes a microphone external to the headset, picking up the voice communication and injecting the voice communication into the electronic communication stream.

In fig. 1, the elements above the line 2 are elements outside the ear cups of the headset. The elements below the cord 2 are inside the ear shell of the headset. Electronic communication terminal 4 is coupled to audio EQ circuit 6 and summer 8. Audio EQ circuit 6 is coupled to summer 10. Summer 10 is coupled to an active noise reduction compensation and gain circuit 12, which is in turn coupled to an "HV" (or ON) switch terminal 14HV of a switch 14. The ambient sound represented by summer 16 includes both acoustic communications and ambient sound noise. Ambient sound enters the earmuffs through two paths; one path includes the talk microphone 18 and the other path is acoustic energy transmitted through the ear cup. The ear cup passively attenuates acoustic energy transmitted through it, as represented by passive attenuation module 20. The talk microphone 18 is coupled to a talk band limiting filter 21 and EQ and gain circuit 22, if present, through an optional switch 24. Talk EQ and gain circuit 22 is coupled to summers 8 and 10. The summer 8 is coupled to the "LV" (or OFF) switch terminal 14LV switch terminal of the switch 14. The terms "HV" and "LV" will be explained below. The driver and ear cup sound characteristics (not separately shown in the figure) are represented as a driver and ear cup acoustic module 26, which couples the switch 14 and the summer 28. The passive attenuation module 20 is coupled to a summer 28, the summer 28 is acoustically coupled to an active noise reduction microphone 30, and the active noise reduction microphone 30 is coupled to the summer 10. The block diagram of fig. 1 shows an exemplary arrangement of elements. Summers 8 and 10 refer to the summation of signals at an element of the circuit of figure 1. Summers 16 and 28 represent the summation of acoustic energy that is generated in the environment and the volume enclosed by the headset, respectively, but not in the circuit elements.

The operation of the ANR headset of fig. 1 will be described in the discussion of fig. 2 and 3.

FIG. 2 illustrates elements of the ANR headphone of FIG. 1 that are active in the "HV" (ON) position of the switch 14. Ambient noise present in the combined acoustic communication and environment is attenuated by the ear cup, as represented by passive attenuation module 20, and becomes part of a feedback loop as described below at summer 28. The electronic communication from the element 4 is equalized in the EQ circuit 6. The signal from the call microphone is band limited at filter 21 and processed by call EQ and gain circuit 22. The equalized electronic communication signal from EQ circuit 6 and the equalized, amplified and band limited talking microphone signal from element 22 are summed at summer 10. The summer 10, ANR compensation and gain circuit 12, driver and acoustic module 26, summer 28, and ANR microphone 30 form a feedback loop as a significant attenuation of the non-corresponding electronic communication signal or amplified and equalized talk-through signal. If the switch 24 is in the OFF position, the talk feature is substantially disabled and the headset operates as a conventional feedback type ANR headset. In some embodiments, element 22 may include a noise reduction element for reducing the content of signals representative of ambient sound noise without reducing the content of signals representative of sound communications. Methods and apparatus for discriminating between voice noise and voice communications are disclosed in U.S. patent 5,768,473, U.S. patent 5,699,436, U.S. patent 5,481,615 and U.S. patent 5,105,377, U.S. patent application 2001/0046304 and U.S. patent application 2002/0141599.

Other ANR headphones may use an ANR circuit in place of a feed-forward (feed forward) circuit of the feedback circuit.

The band limiting filter 21 may be a high pass filter or a band pass filter. The high pass filter will have a cut-off frequency of, for example, 300Hz at approximately the bottom end of the voice frequency band. The band pass filter will have a passband approximating the voice band, e.g., 300Hz to 4.5 kHz. Restricting signals from a talk microphone in the vicinity of the voice band, causing ANR outside the voice band to attenuate noise, while enabling signals representing sound communications at frequencies within the voice band to be communicated with the user. A high pass filter may also be used because most of the noise that is typically desired to cancel is at low frequencies, and because ANR is typically more efficient at low frequencies than at high frequencies.

FIG. 3 shows the elements of the ANR headphone of FIG. 1, which are active when the switch 14 is in the OFF or "LV" position. The active noise reduction feedback loop of fig. 1 and 2 is essentially disabled and the headset operates as a "talk" headset. The sound corresponding to the band-limited equalized and amplified signal from the talking microphone radiates toward the user's ear. The band limiting through the filter 21 encourages the user to hear the sound communication while still maintaining the passive attenuation represented by the passive attenuation module 20. With the switch 24 in the OFF position, the talk feature is disabled and the headset operates as a passive headset. With the circuit of fig. 1 and the switch 14 in the LV or OFF position, the electronic communication terminal 4 can be active. In some embodiments, as described below, the LV switch position may be associated with a state where no signal is present at the electronic communication terminal 4, so the electronic communication terminal and the coupling to the summer 8 are shown in dashed lines. In other implementations, the circuit may be configured such that the electronic communication circuit functions if the ANR circuit is not functioning.

Switches 14 and 24 may be manual or automatic switches. In one implementation, switch 24 is omitted such that the headset has talk capability in either the HV position (as in fig. 2) or the LV position (as in fig. 3) via switch 14. In one implementation, the switch 14 is an automatic switch. If sufficient power is provided to the headphones to operate the ANR circuit, the headphones operate in the manner shown in FIG. 2. If power is provided to the headset that is insufficient to operate the ANR power but sufficient to operate the talk-through circuit, the headset operates in the manner shown in FIG. 3. If the power is insufficient to operate the ANR circuit or the talk circuit, the headset can operate as a passive noise reducing headset, similar to the headset of FIG. 3, with the switch 24 in the OFF position. Since measuring power is most conveniently done by measuring the voltage provided to the headset, "HV" refers to high voltage and "LV" refers to low voltage. The headset may be configured so that it can connect a communication device, such as a console, an intercom (intercom) or a receptacle in the vehicle, that provides power to operate the ANR circuit and communication signals to the headset; the headset therefore does not receive the electronic communication signal if the headset is not connected to the communication device. If the headset is not connected to the communication device, the headset operates as a talk headset if power (e.g., a battery) sufficient to operate the talk circuitry is provided, or operates as a passive headset if power is not provided sufficient to operate the talk circuitry.

The headphones according to fig. 1-3 provide advantages over conventional talk-capable ANR headphones. Can provide the user with: ANR with or without call capability; or a talk-through capability with or without ANR; or passive attenuation with neither ANR nor talk-through capability. The switch may be manual, allowing the user to select a desired combination of features, or may be implemented in an automatic manner, such that, for example, the user selects a feature by connecting or disconnecting the headset to or from the communication device or power source.

Referring to fig. 4A-4E, circuit schematic diagrams of implementing the active noise reduction headphones of fig. 1-3 are illustrated. Fig. 4A is an upper left portion, an upper right portion, a lower right portion, and a lower left portion of the circuit, respectively. The circuit of fig. 4E is shown connected to the circuit portion of fig. 4A at points "a" and "K". The points "L" and "M" connect elements that are not germane to this specification. The circuit elements implementing the modules of fig. 1-3 are surrounded by dashed lines.

The particular devices and techniques disclosed herein can be used and are apart from the inventive concept in which the various elements are arranged in a different order. Thus, the present invention is explained as: including each and every novel feature and each and every novel combination of features disclosed herein and limited only by the spirit and scope of the claims.

Claims (16)

1. A noise reducing headset, comprising:

an active noise reduction signal processing path for providing active noise reduction;

a call signal processing path for providing call capability; and

and a switching element for disabling one or both of the noise reduction signal path and the call signal path.

2. The noise reducing headphone of claim 1, wherein the switching element is for disabling the noise reducing signal path, and wherein the switching element is constructed and arranged to be automatically responsive to power supplied to the switching element.

3. The noise reducing headphone of claim 2, wherein the switching element disables the noise reducing signal path when the power applied to the switching element is insufficient to operate the noise reducing signal path.

4. The noise reduction circuit of claim 1, wherein the telephony signal path includes a microphone and a frequency selective filter for filtering input from the microphone, the filter constructed and arranged to substantially attenuate frequencies below the voice band.

5. The noise reduction circuit of claim 1, wherein the filter is further constructed and arranged to substantially attenuate frequencies not in the voice band.

6. A noise reducing headphone, comprising:

a first signal path including active noise reduction and telephony;

a second signal path including telephony without active noise reduction;

a selection circuit constructed and arranged to select either the first signal path or the second signal path.

7. A noise reducing headphone, comprising:

a third signal path including active noise reduction and not including telephony, wherein the selection circuit is constructed and arranged to select one of the first signal path, the second signal path, or the third signal path.

8. A noise reducing headphone, comprising:

an active noise reduction signal path; and

a call signal path including

Microphone and

a frequency selective filter for filtering input from the microphone, the filter constructed and arranged to significantly attenuate frequencies not in the speech band.

9. The noise reducing headphone of claim 8, wherein the frequency selective filter is a high pass filter.

10. The noise reducing headphone of claim 8, wherein the frequency selective filter is a band pass filter.

11. The noise reducing headset of claim 8, further comprising an element for removing noise from a signal in a talk signal path.

12. A method of operating a noise reducing headset, the noise reducing headset including an active noise reducing signal path and a talk signal path, the method comprising:

providing power to an active noise reduction control signal path and a talk signal path;

the noise reduction control signal path is disabled if power to the path of the active noise reduction control signal is below a first threshold level.

13. The method for operating a noise reducing headset according to claim 12, wherein if the power provided to the active noise reducing control signal path and the talk signal path is above the second threshold, the active noise reducing control signal path is disabled and the headset is operated as a talk headset.

14. The method for operating a noise reducing headset according to claim 13, wherein if the power provided to the path of the active noise reducing control signal and the path of the talk signal is below the second threshold frequency, disabling the talk signal path and operating the headset as a passive noise reducing headset.

15. The method for operating a noise reducing headset according to claim 12, wherein providing power to the active noise reduction control signal path and the talk signal path includes providing power to the noise reduction control signal path from a source external to the headset.

16. A noise reducing headset comprising a telephony signal path including elements for receiving a signal representing ambient sound including ambient sound noise and a voice communication, the telephony signal path including noise removing elements for reducing the ambient noise content of the signal without reducing the voice communication portion of the signal.