Acoustic characterization of an unknown microphone
An electronic device with a microphone is used to determine a transfer function of an environment (and, more generally, an acoustic characteristic). In particular, the electronic device may use the microphone to perform acoustic measurements when the electronic device is proximate to a speaker in the environment. Then, based on the acoustic measurements and a first predetermined transfer function of the speaker, the electronic device may calculate a transfer function of the microphone in a band of frequencies. Moreover, the electronic device may use the microphone to perform additional acoustic measurements in the environment that includes the speaker. Next, based on the additional acoustic measurements, the transfer function of the microphone and a second predetermined transfer function of the speaker, the electronic device may determine the transfer function of the environment in the same or a different band of frequencies.
1. An electronic device, comprising:
a microphone;
a display;
a processor coupled to the microphone and the display;
memory, coupled to the processor, configured to store a program module, wherein, when executed by the processor, the program module causes the electronic device to:
provide, via the display, an instruction to position the electronic device proximate to a speaker in an environment, wherein the position is associated with a near field of the speaker and is in front of the speaker;
perform, using the microphone, acoustic measurements in the environment;
calculate, based at least in part on the acoustic measurements and a first predetermined transfer function of the speaker, a transfer function of the microphone in a first band of frequencies, wherein, prior to the calculation, the transfer function of the microphone is unknown, and
wherein the acoustic measurements used in the calculation are only performed by the electronic device;
provide, via the display, another instruction to position the electronic device at other locations in the environment, wherein the other locations are associated with a far field of the speaker;
perform, using the microphone, additional acoustic measurements in the environment; and
determine, based at least in part on the additional acoustic measurements, the transfer function of the microphone and a second predetermined transfer function of the speaker, a transfer function of the environment in a second band of frequencies.
2. The electronic device of claim 1 , wherein calculating the transfer function of the microphone involves:
determining parameters for a set of predefined transfer functions based at least in part on the acoustic measurements and the first predetermined transfer function of the speaker;
calculating errors between the acoustic measurements and the set of predefined transfer functions; and
selecting a predefined transfer function based at least in part on the errors as the transfer function of the microphone.
3. The electronic device of claim 1 , wherein the environment includes a room and the transfer function of the environment characterizes room modes.
4. The electronic device of claim 1 , wherein the electronic device further comprises an interface circuit configured to communicate with the speaker; and
wherein, when executed by the processor, the program module causes the electronic device to transmit information to the speaker that specifies one of: the transfer function of the environment, one or more extrema in the transfer function of the environment, and a correction for the one or more extrema.
5. The electronic device of claim 1 , wherein the first band of frequencies is different than the second band of frequencies.
6. The electronic device of claim 1 , wherein the other locations are different than a location of the electronic device during the acoustic measurements.
7. The electronic device of claim 1 , wherein the other locations are other than proximate to the speaker.
8. The electronic device of claim 1 , wherein the electronic device includes one of: a remote control, and a cellular telephone.
9. The electronic device of claim 1 , wherein the other instruction includes an instruction to move with the electronic device in the environment.
10. The electronic device of claim 1 , wherein, when executed by the processor, the program module causes the electronic device to trigger the speaker to output predefined acoustic information; and
wherein calculating one of the transfer function of the microphone and the transfer function of the environment is further based at least in part on the predefined acoustic information.
11. A non-transitory computer-readable storage medium for use with an electronic device, the computer-readable storage medium storing a program module that, when executed by the electronic device, causes the electronic device to:
provide an instruction to position the electronic device proximate to a speaker in an environment, wherein the position is associated with a near field of the speaker and is in front of the speaker;
perform, using a microphone in the electronic device, acoustic measurements in the environment;
calculate, based at least in part on the acoustic measurements and a first predetermined transfer function of the speaker, a transfer function of the microphone in a first band of frequencies, wherein, prior to the calculation, the transfer function of the microphone is unknown, and
wherein the acoustic measurements used in the calculation are only performed by the electronic device;
provide another instruction to position the electronic device at other locations in the environment, wherein the other locations are associated with a far field of the speaker;
perform, using the microphone, additional acoustic measurements in the environment; and
determine, based at least in part on the additional acoustic measurements, the transfer function of the microphone and a second predetermined transfer function of the speaker, a transfer function of the environment in a second band of frequencies.
12. The computer-readable storage medium of claim 11 , wherein calculating the transfer function of the microphone involves:
determining parameters for a set of predefined transfer functions based at least in part on the acoustic measurements and the first predetermined transfer function of the speaker;
calculating errors between the acoustic measurements and the set of predefined transfer functions; and
selecting a predefined transfer function based at least in part on the errors as the transfer function of the microphone.
13. The computer-readable storage medium of claim 11 , wherein the environment includes a room and the transfer function of the environment characterizes room modes.
14. The computer-readable storage medium of claim 11 , wherein, when executed by the processor, the program module causes the electronic device to transmit information to the speaker that specifies one of: the transfer function of the environment, one or more extrema in the transfer function of the environment, and a correction for the one or more extrema.
15. The computer-readable storage medium of claim 11 , wherein the first band of frequencies is different than the second band of frequencies.
16. The computer-readable storage medium of claim 11 , wherein the other locations are other than proximate to the speaker.
17. The computer-readable storage medium of claim 11 , wherein the electronic device includes one of: a remote control, and a cellular telephone.
18. The computer-readable storage medium of claim 11 , wherein the other instruction includes an instruction to move with the electronic device in the environment.
19. The computer-readable storage medium of claim 11 , wherein, when executed by the processor, the program module causes the electronic device to trigger the speaker to output predefined acoustic information; and
wherein calculating one of the transfer function of the microphone and the transfer function of the environment is further based at least in part on the predefined acoustic information.
20. A method for determining a transfer function of an environment, comprising:
by an electronic device:
providing an instruction to position the electronic device proximate to a speaker in the environment, wherein the position is associated with a near field of the speaker and is in front of the speaker;
performing, using a microphone in the electronic device, acoustic measurements in the environment;
calculating, based at least in part on the acoustic measurements and a first predetermined transfer function of the speaker, a transfer function of the microphone in a first band of frequencies, wherein, prior to the calculation, the transfer function of the microphone is unknown, and
wherein the acoustic measurements used in the calculation are only performed by the electronic device;
providing another instruction to position the electronic device at other locations in the environment, wherein the other locations are associated with a fax field of the speaker;
performing, using the microphone, additional acoustic measurements in the environment; and
determining, based at least in part on the additional acoustic measurements, the transfer function of the microphone and a second predetermined transfer function of the speaker, a transfer function of the environment in a second band of frequencies.
21. The electronic device of claim 1 , wherein the speaker includes a subwoofer and the first band of frequencies is associated with the subwoofer.
22. The computer-readable storage medium of claim 11 , wherein the speaker includes a subwoofer and the first band of frequencies is associated with the subwoofer.
23. The method of claim 20 , wherein the speaker includes a subwoofer and the first band of frequencies is associated with the subwoofer.