Systems and methods of adjusting bass levels of multi-channel audio signals
Systems and methods for adjusting bass levels of a multi-channel audio signal include, among other features, (i) receiving the multi-channel signal via a playback device; (ii) separating, from the multi-channel signal, low-frequency signals comprising frequencies less than a threshold frequency; (iii) determining electrical energies of the low-frequency signals; (iv) determining a first energy by summing the electrical energies of the low-frequency signals; (v) consolidating the low-frequency signals into a consolidated low-frequency signal; (vi) determining a second energy by determining an electrical energy of the consolidated low-frequency signal; (vii) generating a gain-adjusted low-frequency signal by adjusting a gain of the consolidated low-frequency signal based on both (a) the first energy and (b) the second energy; (viii) generating a gain-adjusted multi-channel signal by mixing the gain-adjusted low-frequency signal back into the multi-channel signal; and (ix) using the gain-adjusted multi-channel signal to play back gain-adjusted multi-channel audio content via the playback device.
1. A playback device comprising:
a plurality of audio drivers;
one or more processors;
tangible, non-transitory, computer-readable media storing instructions executable by the one or more processors, wherein the instructions, when executed, cause the playback device to perform operations comprising:
receiving a multi-channel audio signal comprising a set of audio channels;
for each channel in the set of audio channels, applying a low pass filter to the channel to obtain a low-frequency component of the channel comprising audio information below a threshold frequency;
combining the low-frequency component of each channel into a consolidated low frequency signal;
adjusting a gain of the consolidated low frequency signal to generate a gain-adjusted consolidated low frequency signal;
for each channel in the set of audio channels, mixing the gain-adjusted consolidated low frequency signal with audio content of the channel above the threshold frequency to generate a gain-adjusted channel;
playing the individual gain-adjusted channels via the plurality of audio drivers;
wherein the set of channels in the multi-channel audio signal comprises a left-channel audio signal, a center-channel audio signal, and a right-channel audio signal, and wherein for each channel in the set of audio channels, applying a low pass filter to the channel to obtain a low-frequency component of the channel comprising audio information below a threshold frequency comprises:
low pass filtering the left-channel audio signal to obtain a low-frequency component of the left-channel audio signal comprising audio information below the threshold frequency;
low pass filtering the right-channel audio signal to obtain a low-frequency component of the right-channel audio signal comprising audio information below the threshold frequency; and
low pass filtering the center-channel audio signal to obtain a low-frequency component of the center-channel audio signal comprising audio information below the threshold frequency.
2. The playback device of claim 1 , wherein adjusting a gain of the consolidated low frequency signal to generate a gain-adjusted consolidated low frequency signal comprises:
for each channel in the set of audio channels, determining an electrical energy of the low frequency component of the channel;
determining a first energy representing a sum of the electrical energies of the low frequency components of the channels in the set of audio channels;
determining a second energy representing an electrical energy of a sum of the low frequency components of the channels in the set of audio channels; and
generating the gain-adjusted consolidated low frequency signal based on both (i) the first energy and (ii) the second energy.
3. The playback device of claim 2 , wherein adjusting a gain of the consolidated low frequency signal to generate a gain-adjusted consolidated low frequency signal comprises adjusting a gain of the consolidated low frequency signal according to:
G=E 1 /E 2 ,
wherein G is the gain adjustment of the consolidated low frequency signal, E 1 is the first energy, and E 2 is the second energy.
4. The playback device of claim 1 , wherein adjusting a gain of the consolidated low frequency signal to generate a gain-adjusted consolidated low frequency signal reduces a volume of any audio content that includes the gain-adjusted consolidated low frequency signal that is played by the playback device.
5. The playback device of claim 1 , wherein each channel in the multi-channel audio signal corresponds to a sound axis, and wherein playing the individual gain-adjusted channels via the plurality of audio drivers comprises:
playing each gain-adjusted channel via a sound axis corresponding to the channel.
6. The playback device of claim 1 , wherein the plurality of audio drivers includes a first audio driver and a second audio driver, and wherein a value of the threshold frequency is based on a distance between the first and second audio drivers.
7. The playback device of claim 6 , wherein the distance between the first and second audio drivers is an odd-integer multiple of a quarter-wavelength of the threshold frequency.
8. Tangible, non-transitory, computer-readable media storing instructions executable by one or more processors, wherein the instructions, when executed, cause a playback device to perform operations comprising:
receiving a multi-channel audio signal comprising a set of audio channels;
for each channel in the set of audio channels, applying a low pass filter to the channel to obtain a low-frequency component of the channel comprising audio information below a threshold frequency;
combining the low-frequency component of each channel into a consolidated low frequency signal;
adjusting a gain of the consolidated low frequency signal to generate a gain-adjusted consolidated low frequency signal;
for each channel in the set of audio channels, mixing the gain-adjusted consolidated low frequency signal with audio content of the channel above the threshold frequency to generate a gain-adjusted channel;
playing the individual gain-adjusted channels via a plurality of audio drivers;
wherein the set of channels in the multi-channel audio signal comprises a left-channel audio signal, a center-channel audio signal, and a right-channel audio signal, and wherein for each channel in the set of audio channels, applying a low pass filter to the channel to obtain a low-frequency component of the channel comprising audio information below a threshold frequency comprises:
low pass filtering the left-channel audio signal to obtain a low-frequency component of the left-channel audio signal comprising audio information below the threshold frequency;
low pass filtering the right-channel audio signal to obtain a low-frequency component of the right-channel audio signal comprising audio information below the threshold frequency; and
low pass filtering the center-channel audio signal to obtain a low-frequency component of the center-channel audio signal comprising audio information below the threshold frequency.
9. The tangible, non-transitory computer readable media of claim 8 , wherein adjusting a gain of the consolidated low frequency signal to generate a gain-adjusted consolidated low frequency signal comprises:
for each channel in the set of audio channels, determining an electrical energy of the low frequency component of the channel;
determining a first energy representing a sum of the electrical energies of the low frequency components of the channels in the set of audio channels;
determining a second energy representing an electrical energy of a sum of the low frequency components of the channels in the set of audio channels; and
generating the gain-adjusted consolidated low frequency signal based on both (i) the first energy and (ii) the second energy.
10. The tangible, non-transitory computer readable media of claim 9 , wherein adjusting a gain of the consolidated low frequency signal to generate a gain-adjusted consolidated low frequency signal comprises adjusting a gain of the consolidated low frequency signal according to:
G=E 1 /E 2 ,
wherein G is the gain adjustment of the consolidated low frequency signal, E 1 is the first energy, and E 2 is the second energy.
11. The tangible, non-transitory computer readable media of claim 8 , wherein adjusting a gain of the consolidated low frequency signal to generate a gain-adjusted consolidated low frequency signal reduces a volume of any audio content that includes the gain-adjusted consolidated low frequency signal that is played by the playback device.
12. The tangible, non-transitory computer readable media of claim 8 , wherein each channel in the multi-channel audio signal corresponds to a sound axis, and wherein playing the individual gain-adjusted channels via the plurality of audio drivers comprises:
playing each gain-adjusted channel via a sound axis corresponding to the channel.
13. The tangible, non-transitory computer readable media of claim 8 , wherein the plurality of audio drivers includes a first audio driver and a second audio driver, and wherein a value of the threshold frequency is based on a distance between the first and second audio drivers.
14. The tangible, non-transitory computer readable media of claim 13 , wherein the distance between the first and second audio drivers is an odd-integer multiple of a quarter-wavelength of the threshold frequency.
15. A method performed by a playback device, the method comprising:
receiving a multi-channel audio signal comprising a set of audio channels;
for each channel in the set of audio channels, applying a low pass filter to the channel to obtain a low-frequency component of the channel comprising audio information below a threshold frequency;
combining the low-frequency component of each channel into a consolidated low frequency signal;
adjusting a gain of the consolidated low frequency signal to generate a gain-adjusted consolidated low frequency signal;
for each channel in the set of audio channels, mixing the gain-adjusted consolidated low frequency signal with audio content of the channel above the threshold frequency to generate a gain-adjusted channel;
playing the individual gain-adjusted channels via a plurality of audio drivers;
wherein the set of channels in the multi-channel audio signal comprises a left-channel audio signal, a center-channel audio signal, and a right-channel audio signal, and wherein for each channel in the set of audio channels, applying a low pass filter to the channel to obtain a low-frequency component of the channel comprising audio information below a threshold frequency comprises:
low pass filtering the left-channel audio signal to obtain a low-frequency component of the left-channel audio signal comprising audio information below the threshold frequency;
low pass filtering the right-channel audio signal to obtain a low-frequency component of the right-channel audio signal comprising audio information below the threshold frequency; and
low pass filtering the center-channel audio signal to obtain a low-frequency component of the center-channel audio signal comprising audio information below the threshold frequency.
16. The method of claim 15 , wherein adjusting a gain of the consolidated low frequency signal to generate a gain-adjusted consolidated low frequency signal comprises:
for each channel in the set of audio channels, determining an electrical energy of the low frequency component of the channel;
determining a first energy representing a sum of the electrical energies of the low frequency components of the channels in the set of audio channels;
determining a second energy representing an electrical energy of a sum of the low frequency components of the channels in the set of audio channels; and
generating the gain-adjusted consolidated low frequency signal based on both the first energy and the second energy according to:
G=E 1 /E 2 ,
wherein G is the gain adjustment of the consolidated low frequency signal, E 1 is the first energy, and E 2 is the second energy.