Sound processing device, sound processing method, and computer program
[Object] To provide a sound processing device capable of effectively reducing ambient noise at low cost. [Solution] Provided is a sound processing device including: a first sound collector configured to collect a first noise signal from a noise source of noise leaking into a casing mounted to a user's ear; a first signal processing unit configured to form a first noise reduction signal used to reduce noise at a cancellation point on the basis of the first noise signal; a second signal processing unit configured to form a second noise reduction signal used to reduce noise at a cancellation point with respect to a first pseudo noise signal; an adder configured to add the first noise reduction signal and the second noise reduction signal; and a sound emitter configured to emit an output of the adder into the casing as sound. The first pseudo noise signal is a signal obtained by subtracting an output of the adder applied with a simulation transfer characteristic from an output of the first sound collector, the simulation transfer characteristic being obtained by simulating a transfer characteristic from the sound emitter to the first sound collector.
1. A sound processing device comprising:
a first sound collector configured to collect a first noise signal from a noise source of noise leaking into a casing mounted to a user's ear;
a first filter circuit configured to generate a first noise reduction signal used to reduce noise at a predetermined cancellation point based on the first noise signal;
a second filter circuit configured to generate a second noise reduction signal used to reduce noise at the predetermined cancellation point based on a first pseudo noise signal;
a second sound collector being provided outside the casing and configured to collect a second noise signal from the noise source;
a third filter circuit configured to generate a third noise reduction signal used to reduce noise at the predetermined cancellation point based on the second noise signal collected by the second sound collector;
an adder configured to add the first noise reduction signal, the second noise reduction signal and the third noise reduction signal; and
a sound emitter configured to emit an output of the adder into the casing as sound,
wherein the first pseudo noise signal is a signal obtained by subtracting a first simulation transfer output, determined by applying a simulation transfer characteristic to an output of the adder, from an output of the first sound collector, the simulation transfer characteristic being obtained by simulating a transfer characteristic from the sound emitter to the first sound collector.
2. The sound processing device according to claim 1 , further comprising:
an analyzer configured to analyze the second noise signal; and
a selection unit configured to select a filter to be used by at least any one of the first to third filter circuits on a basis of an analysis result obtained by the analyzer.
3. The sound processing device according to claim 1 , further comprising:
an analyzer configured to analyze the first pseudo noise signal; and
a selection unit configured to select a filter to be used by at least any one of the first to third filter circuits on a basis of an analysis result obtained by the analyzer.
4. The sound processing device according to claim 3 , comprising:
a changing unit configured to change gradually an output in switching between a first filter and a second filter.
5. The sound processing device according to claim 1 ,
wherein the first filter circuit includes n (where n is an integer of 2 or more) filters, and
the n filters each generate an n-th noise reduction signal on a basis of an n-th pseudo noise signal obtained by subtracting a second simulation transfer output, determined by applying a simulation transfer characteristic to an output of the first filter circuit, from the output of the first sound collector.
6. The sound processing device according to claim 1 , further comprising:
a fourth filter circuit configured to apply the simulation transfer characteristic to the third noise reduction signal,
wherein the first filter circuit generates the first noise reduction signal based on a result obtained by subtracting an output of the fourth filter circuit from the first noise signal.
7. The sound processing device according to claim 6 ,
wherein the fourth filter circuit applies the simulation transfer characteristic to an external sound signal.
8. The sound processing device according to claim 1 , comprising:
a detection unit configured to detect a state of the first pseudo noise signal; and
an adjustment unit configured to adjust the output of the adder on a basis of a detection result obtained by the detection unit.
9. The sound processing device according to claim 8 ,
wherein the detection unit detects the state of the first pseudo noise signal on a basis of an external sound signal.
10. A sound processing method comprising:
collecting, by a first sound collector, a first noise signal from a noise source of noise leaking into a casing mounted to a user's ear;
generating a first noise reduction signal used to reduce noise at a predetermined cancellation point based on the first noise signal;
generating a second noise reduction signal used to reduce noise at the predetermined cancellation point based on a first pseudo noise signal;
collecting, by a second sound collector provided outside the casing, a second noise signal from the noise source;
generating a third noise reduction signal used to reduce noise at the predetermined cancellation point based on the second noise signal collected by the second sound collector;
adding the first noise reduction signal, the second noise reduction signal and the third noise reduction signal to generate an added signal;
emitting, by a sound emitter, the added signal into the casing as sound; and
applying a simulation transfer characteristic to the added signal to generate a simulation transfer output, the simulation transfer characteristic being obtained by simulating a transfer characteristic from the sound emitter to the first sound collector,
wherein the first pseudo noise signal is a signal obtained by subtracting the simulation transfer output from an output of the first sound collector.
11. A non-transitory computer readable medium containing computer readable instructions that, when executed by a computer, perform a sound processing method comprising:
generating a first noise reduction signal used to reduce noise at a predetermined cancellation point based on a first noise signal from a noise source of noise leaking into a casing mounted to a user's ear, the first noise signal being collected by a first sound collector;
generating a second noise reduction signal used to reduce noise at the predetermined cancellation point based on a first pseudo noise signal;
generating a third noise reduction signal used to reduce noise at the predetermined cancellation point based on a second noise signal collected by a second sound collector provided outside the casing;
adding the first noise reduction signal, the second noise reduction signal and the third noise reduction signal to generate an added signal;
emitting, by a sound emitter, the added signal into the casing as sound; and
applying a simulation transfer characteristic to the added signal to generate a simulation transfer output, the simulation transfer characteristic being obtained by simulating a transfer characteristic from the sound emitter to the first sound collector,
wherein the first pseudo noise signal is a signal obtained by subtracting the simulation transfer output from an output of the first sound collector.