Frequency expansion for synthesizer
View Patent ↗A method is provided for generating synthetic audio signals with a synthesizer by generating a synthesizer output signal with a low sampling rate of the synthesizer. Because of the low sampling rate, missing high-frequency components of the synthesizer output signal are generated by adding a high-frequency signal. An amplitude-modulated high-frequency signal is preferred, and the amplitude-modulated signal S and synthesizer output signal are converted to a higher sampling rate.
1. A method for generating synthetic audio signals, the method comprising:
providing a synthesizer for generating a synthesizer output signal with a low sampling rate of the synthesizer;
generating missing high frequency components of the synthesizer output signal, due to the low sampling rate, by adding a high-frequency signal, wherein
modulating an amplitude of the high-frequency signal; and
converting the amplitude-modulated signal and the synthesizer output signal to a respectively higher sampling rate, wherein
a common sampling rate conversion is used for conversation to the high sampling rate, with the synthesizer output signal being simultaneously converted to frequencies from 0 Hz up to a Nyquist frequency of the low sampling rate, and the amplitude-modulated signal is converted to frequencies from the Nyquist frequency of the low sampling rate up to the Nyquist frequency of the high sampling rate.
2. A method for generating synthetic audio signals as claimed in claim 1 , wherein the low sampling rate is 16 kHz.
3. A method for generating synthetic audio signals as claimed in claim 1 , wherein the amplitude modulation occurs at a low sampling rate.
4. A. method for generating synthetic audio signals as claimed in claim 3 , wherein the low sampling rate is 16 kHz.
5. A method for generating synthetic audio signals as claimed in claim 1 , wherein the high sampling rate is 32 kHz.
6. A method for generating synthetic audio signals as claimed in claim 1 , wherein the high-frequency signal is noise.
7. A method for generating synthetic audio signals as claimed in claim 1 , wherein the high-frequency signal is calculated at a low sampling rate.
8. A method for generating synthetic audio signals as claimed in claim 7 , wherein the low sampling rate is 16 kHz.
9. A method for generating synthetic audio signals as claimed in claim 1 , wherein the high-frequency signal is one of a sound mixture and a single sound.
10. A method for generating synthetic audio signals as claimed in claim 1 , wherein the high-frequency signal is a sinusoidal signal.
11. A method for generating synthetic audio signals as claimed in claim 1 , further comprising measuring a power of the high-frequency components present in the synthesizer output signal.
12. A method for generating synthetic audio signals as claimed in claim 11 , wherein the power of the high-frequency components is in a range from 4 kHz and 8 kHz.
13. A method for generating synthetic audio signals as claimed in claim 11 , wherein the power of the high-frequency components is used for calculating an amplitude of the high-frequency signal.
14. A method for generating synthetic audio signals as claimed in claim 1 , wherein the method is employed in a mobile terminal.
15. A method for generating synthetic audio signals as claimed in claim 14 , wherein the mobile terminal is a mobile telephone.
16. A system for generating synthetic audio signals, the comprising:
a synthesizer for generating a synthesizer output signal with a low sampling rate of the synthesizer, wherein
missing high frequency components of the synthesizer output signal are generated, due to the low sampling rate, by adding a high-frequency signal,
an amplitude of the high-frequency signal is modulated, and
the amplitude-modulated signal and the synthesizer output signal are converted to a respectively higher sampling rate, wherein
a common sampling rate conversion is used for conversation to the high sampling rate, with the synthesizer output signal being simultaneously converted to frequencies from 0 Hz up to a Nyquist frequency of the low sampling rate, and the amplitude-modulated signal is converted to frequencies from the Nyquist frequency of the low sampling rate up to the Nyquist frequency of the high sampling rate.
17. A mobile device with an apparatus for generating synthetic audio signals, the apparatus comprising:
a synthesizer for generating a synthesizer output signal with a low sampling rate of the synthesizer, and generating missing high frequency components of the synthesizer output signal, due to the low sampling rate, by adding a high-frequency signal; and
a modulator to modulate an amplitude of the high-frequency signal to produce an amplitude-modulated signal, wherein
a common sampling rate conversion is used for conversion to a high sampling rate, with the synthesizer output signal being simultaneously converted to frequencies from 0 Hz up to a Nyquist frequency of the low sampling rate, and the amplitude-modulated signal is converted to frequencies from the Nyquist frequency of the low sampling rate up to a Nyquist frequency of the high sampling rate.