An audio system includes a channel ( 10 ) for processing signals. The channel ( 10 ) includes a processing module ( 50 ) that follows a chain of modules ( 40 ) wherein the chain ( 40 ) includes a preceding processing module ( 45 ). The following processing module ( 50 ) is coupled to the preceding processing module ( 45 ) in the chain of modules ( 40 ) for receiving the output signal ( 25 ). The channel ( 10 ) further includes a combiner ( 60 ). The combiner ( 60 ) has two inputs, a first input ( 65 ) receives the signal ( 30 ) to be processed in the channel ( 10 ), and a second input ( 70 ) receives a reference signal ( 75 ). The combiner ( 60 ) further includes an output ( 80 ) coupled to an input of the preceding processing module ( 45 ) in the chain ( 40 ). By coupling a combination of the signal ( 30 ) to be processed and the reference signal ( 75 ) to the input ( 55 ) of the preceding processing module ( 45 ) in the chain ( 40 ) and by having a correction signal ( 90 ) from the processing unit ( 85 ) generated in response to a modification of the reference signal ( 75 ) in the output signal ( 25 ) of the preceding processing module ( 45 ) in the chain ( 40 ), the amount and type of processing in the preceding processing module ( 45 ) in the chain ( 40 ) can be estimated in the processing unit ( 85 ) and be corrected for in the following processing module ( 50 ).
1. An audio system including a channel for processing signals, the channel comprising:
a preceding processing module, wherein the preceding processing module comprises a volume control module;
a following processing module being coupled to the preceding processing module configured to receive an output signal from the preceding processing module, wherein the following processing module comprises an automatic gain control module;
a combiner having a first input configured to receive a signal to be processed by the channel, a second input configured to receive a reference signal, and an output coupled to an input of the preceding processing module; and
a processing unit configured to receive the output signal, wherein the processing unit is configured to generate a correction signal in response to a modification of the reference signal in the output signal and the following processing module is configured to change a processing of the following processing module in response to the correction signal.
2. The audio system according to claim 1 , further comprising:
at least one further channel, wherein the reference signal is identical for each further channel.
3. The audio system according to claim 1 , further comprising:
at least one further channel, wherein the reference signal is different for each further channel.
4. The audio system according to claim 1 , further comprising:
a filter having an input configured to receive the signal to be processed by the channel and having an output coupled to the first input.
5. The audio system according to claim 4 , wherein the reference signal is a sine wave of a predetermined frequency and the filter is designed for attenuating frequency components that are an integer multiple of the predetermined frequency.
6. The audio system according to claim 4 , wherein the reference signal is a signal having multi-frequency components and the filter is designed for attenuating frequency components that are an integer multiple, a sum, and a difference of any integer multiple of the multi-frequency components.
7. The audio system according to claim 1 , wherein the reference signal is a sine wave.
8. The audio system according to claim 1 wherein the reference signal is a signal having multi-frequency sine wave components.
9. The audio system according to claim 6 wherein the signal having multi-frequency components is a signal having multi-frequency sine wave components.
10. The audio system according to claim 4 , wherein the filter is a notch filter.
11. A digital signal audio processing system comprising the audio system according to claim 1 .
12. A method of processing audio signals in an audio system having a series of processing modules, the method comprising:
combining a signal to be processed by the series of processing modules with a reference signal to obtain a combined signal;
processing the combined signal in a preceding processing module, wherein the preceding processing module comprises a volume control module, to obtain an output signal;
processing the output signal in a following processing module, wherein the following processing module comprises an automatic gain control module, in the series of processing modules;
generating a correction signal in response to a modification of the reference signal in the output signal; and
changing a processing of the following processing module in response to the correction signal.
13. A digital signal audio processing system working according to the method of claim 12 .