Bass enhancement system
A bass enhancement system can provide an enhanced bass effect for speakers, including relatively small speakers. The bass enhancement system can apply one or more bass enhancements to an input audio signal. For example, the bass enhancement system can exploit how the human ear processes overtones and harmonics of low-frequency sounds to create the perception that non-existent (or attenuated) low-frequency sounds are being emitted from a loudspeaker. The bass enhancement system can generate harmonics of at least some low-frequency fundamental frequencies in one embodiment. Playback of at least some harmonics of a low-frequency fundamental frequency can cause a listener to perceive the playback of the low-frequency fundamental frequency. Advantageously, in certain embodiments, the bass enhancement system can generate these harmonics without performing processing-intensive pitch-detection techniques or the like to identify the fundamental frequencies.
1. A system for enhancing bass audio, the system comprising:
a bass enhancer implemented using one or more hardware processors, the bass enhancer comprising:
a harmonic generator module configured to generate harmonics of one or more bass frequencies of an input audio signal based at least in part on available headroom in the input audio signal, and
an early reflections module configured to filter the input audio signal with a tapped delay line having one or more tap delays, wherein the early reflections module is further configured to randomize one or both of the one or more tap delays and the coefficients of the tapped delay line;
wherein the base enhancer generates a first output signal based at least in part upon an output signal of the harmonic generator module and an output signal of the early reflections module;
an equalizer configured to emphasize frequencies in the input audio signal comprising lowest reproducible frequencies of a speaker to generate a second output signal;
a combiner configured to generate a combined audio signal based at least in part upon the first output signal and the second output signal; and
a level adjuster configured to adaptively apply a gain to at least a lower band of frequencies in the combined audio signal, wherein the gain depends on available headroom in the combined audio signal.
2. The system of claim 1 , wherein the harmonic generator module is further configured to generate the harmonics by at least:
determining the available headroom in the input audio signal; and
applying a second gain to approximately half of the input audio signal, the second gain being greater than the available headroom in the input audio signal and thereby generating harmonics of one or more fundamental bass frequencies in the input audio signal.
3. The system of claim 1 , wherein the bass enhancer further comprises a loudness filter configured to emphasize the one or more bass frequencies relative to other frequencies in the input audio signal.
4. The system of claim 3 , wherein the loudness filter applies an inverted equal loudness curve to the input audio signal.
5. The system of claim 1 , wherein the tapped delay line is configured to simulate reverberation reproduced by bass frequencies.
6. The system of claim 1 , further comprising a combiner configured to combine output of the bass enhancer with the input audio signal to produce a combiner output, the combiner further configured to provide the combiner output to the equalizer.
7. The system of claim 1 , wherein the level adjuster further comprises a high pass shelving filter configured to restore balance to a band of high frequencies in the input audio signal.
8. A method for enhancing audio, the method comprising:
producing an enhanced audio signal, wherein producing the enhanced audio signal comprises:
generating, with one or more processors, harmonics of first frequencies of an input audio signal, and
filtering the input audio signal with a tapped delay line having one or more tap delays and configured to simulate reverberation reproduced by bass frequencies, wherein one or both of the tap delays and coefficients of the tapped delay line over time are randomized;
emphasizing second frequencies in the input audio signal with an equalization filter to produce an equalized audio signal, the second frequencies corresponding with a speaker size setting of a speaker;
combining the enhanced audio single and the equalized audio signal to form an output audio signal; and
supplying the output audio signal to the speaker.
9. The method of claim 8 , wherein the second frequencies comprise at least some of the first frequencies.
10. The method of claim 8 , wherein the second frequencies comprise a band of frequencies around the speaker size setting.
11. The method of claim 8 , wherein the first frequencies comprise bass frequencies.
12. The method of claim 8 , wherein said generating the harmonics further comprises:
determining available headroom in the input audio signal; and
applying a gain to approximately half of the input audio signal, the gain being greater than the available headroom in the input audio signal and thereby generating harmonics of one or more fundamental bass frequencies in the input audio signal.
13. The method of claim 8 , wherein the input audio signal comprises a downmix of two or more input signals.
14. The method of claim 13 , wherein the two or more input signals comprise two or more of the following: a left front signal, a right front signal, a center signal, a left surround signal, and a right surround signal.
15. Non-transitory physical electronic storage comprising instructions stored thereon that, when executed by one or more processors, cause the one or more processors to implement operations for enhancing bass audio, the operations comprising:
receiving an input audio signal;
determining available headroom in the input audio signal; and
applying a gain to approximately half of the input audio signal to produce a partially-clipped audio signal, the gain being greater than the available headroom in the input audio signal, thereby generating harmonics of one or more bass frequencies in the input audio signal;
filtering the input audio signal with a tapped delay line having one or more tap delays and configured to simulate reverberation reproduced by bass frequencies to produce a filtered audio signal, wherein one or both of the tap delays and coefficients of the tapped delay line over time are randomized; and
combining the partially-clipped audio signal and the filtered audio signal to produce an output signal.
16. The non-transitory physical electronic storage of claim 15 , wherein the operations further comprise: adding the input audio signal to the partially-clipped audio signal to produce a combined audio signal, and emphasizing a band of frequencies in the combined audio signal, the band of frequencies being associated with a speaker size setting.
17. The non-transitory physical electronic storage of claim 15 , in combination with one or more processors.
18. A system for enhancing bass audio, the system comprising:
one or more hardware processors configured to:
access a speaker size setting input by a user;
configure a plurality of bass enhancement parameters of a bass enhancement based at least partly on the speaker size setting;
apply the bass enhancement to a first portion of an audio input signal using the bass enhancement parameters to enhance bass frequencies of the audio input signal, the bass enhancement comprising a filter configured to filter the audio input signal with a tapped delay line comprising a coefficient and a delay;
randomize a value of one or both of the coefficient and the delay; and
apply the bass enhancement to a second portion of the audio input signal based on said randomization.
19. The system of claim 18 , wherein the bass enhancement parameters comprise one or more of the following: a cutoff frequency, a gain, and a bandwidth.
20. The system of claim 18 , wherein the bass enhancement parameters comprise a cutoff frequency of a low pass filter configured to attenuate frequencies above the speaker size setting.
21. The system of claim 18 , wherein the bass enhancement parameters comprise a bandwidth of an equalization filter configured to emphasize a band of frequencies in the audio input signal.