Methods and apparatus for processing audio signals
A method for processing an audio signal (i(t)), comprises: receiving a first set (x(t)) of time-varying signals representing a first sound comprised in the audio signal (i(t)), the first set (x(t)) of time-varying signals comprising an amplitude modulation signal (a(t)), a carrier frequency signal (f c (t)), a pitch signal (f 0 (t)) and an FM index signal (h(t)); and modifying the first set (x(t)) of time-varying signals by modifying the amplitude of the FM index signal (h(t)), thereby providing a first modified set (x′(t)) of time-varying signals. The resulting first modified set (x′(t)) of time-varying signals may subsequently be modulated to provide an audio output signal.
1. A method for processing an audio signal (i(t)) representing a processable representation of a first sound, the method comprising:
receiving a first set (x(t)) of time-varying signals representing a first sound comprised in the audio signal (i(t)), the first set (x(t)) of time-varying signals comprising an amplitude modulation signal (a(t)), a carrier frequency signal (f c (t)), a pitch signal (f 0 (t)) and an FM index signal (h(t));
modifying the first set (x(t)) of time-varying signals by modifying the amplitude of the FM index signal (h(t)), thereby providing a first modified set (x′(t)) of time-varying signals; and
providing a first modulated audio signal (s(t)) which is dependent on the first modified set (x′(t)) of the time-varying signal, wherein
the amplitude modulation signal a(t) controls time-varying amplitude of the modulated audio signal s(t),
the carrier frequency signal f c (t) controls time-varying center frequency of the modulated audio signal s(t),
the pitch signal f 0 (t) controls time-varying spectral distance between sidebands in the frequency modulation of the modulated audio signal s(t), and
the FM index signal h(t) controls time-varying spectral distribution of energy in the modulated audio signal s(t).
2. The method according to claim 1 , wherein modifying the amplitude of the FM index signal (h(t)) comprises amplifying or attenuating the FM index signal (h(t)).
3. The method according to claim 1 , and further comprising:
providing an audible signal in dependence on the first modulated audio signal (s(t)).
4. The method according to claim 1 , and further comprising:
receiving the audio signal (i(t)); and
demodulating the audio signal (i(t)), thereby providing the first set (x(t)) of time-varying signals.
5. The method according to claim 3 , wherein modifying the first set (x(t)) of time-varying signals at least partially compensates for a hearing loss of an individual.
6. The method according to claim 1 , wherein the first sound comprised in the audio signal (i(t)) is speech or a speech formant.
7. The method according to claim 1 , and further comprising:
processing a second sound comprised in the audio signal (i(t)) to provide a second modulated audio signal (s 2 (t), s N (t)); and
combining the first modulated audio signal (s(t), s 1 (t)) and the second modulated audio signal (s 2 (t), s N (t)).
8. The method according to claim 7 , and further comprising:
providing the audible signal in dependence on the combination (c(t)) of the first modulated audio signal (s(t), s 1 (t)) and the second modulated audio signal (s 2 (t), s N (t)).
9. An apparatus comprising:
a signal processor configured to execute a method comprising:
receiving a first set (x(t)) of time-varying signals representing a first sound comprised in the audio signal (i(t)), the first set (x(t)) of time-varying signals comprising an amplitude modulation signal (a(t)), a carrier frequency signal (f c (t)), a pitch signal (f 0 (t) and an FM index signal (h(t));
modifying the first set (x(t)) of time-varying signals by modifying the amplitude of the FM index signal (h(t)), thereby providing a first modified set (x′(t)) of time-varying signals; and
providing a first modulated audio signal (s(t)) which is dependent on the first modified set (x′(t)) of the time-varying signal, wherein
the amplitude modulation signal a(t) controls time-varying amplitude of the modulated audio signal s(t),
the carrier frequency signal f c (t) controls time-varying center frequency of the modulated audio signal s(t),
the pitch signal f 0 (t) controls time-varying spectral distance between sidebands in the frequency modulation of the modulated audio signal s(t), and
the FM index signal h(t) controls time-varying spectral distribution of energy in the modulated audio signal s(t).
10. The apparatus according to claim 9 , and comprising:
a multiplier adapted to modify the first set (x(t)) of time-varying signals to provide the first modified set (x′(t)) of time-varying signals.
11. The apparatus according to claim 9 , further being adapted to provide a first modulated audio signal (s(t)) in dependence on the first modified set (x′(t)) of time-varying signals, and further comprising a modulator adapted to provide the first modulated audio signal (s(t), s 1 (t)).
12. The apparatus according to claim 11 , further being adapted to provide an audible signal in dependence on the first modulated audio signal (s(t)), and further comprising an output transducer adapted to provide the audible signal.
13. The apparatus according to claim 9 , further being adapted to receive the audio signal (i(t)) and demodulate the audio signal (i(t)), thereby providing the first set (x(t)) of time-varying signals, and further comprising a demodulator adapted to demodulate the audio signal (i(t)).
14. The apparatus according to claim 13 , and further comprising:
an input signal path adapted to provide the audio signal (i(t)) to the demodulator in dependence on an acoustic signal, the input signal path comprising an input transducer.
15. The method according to claim 2 , and further comprising:
providing a first modulated audio signal (s(t)) in dependence on the first modified set (x′(t)) of time-varying signals.
16. The method according to claim 2 , and further comprising:
receiving the audio signal (i(t)); and
demodulating the audio signal (i(t)), thereby providing the first set (x(t)) of time-varying signals.
17. The method according to claim 2 , wherein the first sound comprised in the audio signal (i(t)) is speech or a speech formant.
18. The apparatus according to claim 10 , further being adapted to provide a first modulated audio signal (s(t)) in dependence on the first modified set (x′(t)) of time-varying signals, and further comprising a modulator adapted to provide the first modulated audio signal (s(t), s 1 (t)).
19. The apparatus according to claim 10 , further being adapted to receive the audio signal (i(t)) and demodulate the audio signal (i(t)), thereby providing the first set (x(t)) of time-varying signals, and further comprising a demodulator adapted to demodulate the audio signal (i(t)).