System and method for adapting a loudspeaker signal
View Patent ↗A sound system 100 for producing sound on a loudspeaker 130 is provided wherein the temperature of a voice coil of the loudspeaker may be monitored continuously. The sound system comprises a signal generator 150 for generating an evaluation signal which is combined with an input sound signal 120 to obtain a loudspeaker signal and a monitor 140 for monitoring an electric response of the voice coil to the loudspeaker signal. The loudspeaker signal may be adapted 180 to control the temperature of the voice coil in dependency upon the monitored response. The system can determine the temperature of the voice coil 170 even if the input sound signal comprises only little sound energy.
1. A sound system for producing sound, the sound system comprising
a processing unit for processing an input sound signal to produce a loudspeaker signal,
a loudspeaker for generating sound in dependency on the loudspeaker signal, the loudspeaker comprising a voice coil for driving the loudspeaker, a temperature of the voice coil depending on the loudspeaker signal, and
a monitor for monitoring an electric response of the voice coil to the loudspeaker signal, the processing unit being configured for adapting the loudspeaker signal to control the temperature of the voice coil in dependency on the monitored response,
wherein
the processing unit comprises a signal generator for generating an evaluation signal, and processing the input sound signal to produce a loudspeaker signal involves combining the evaluation signal with the input sound signal, wherein the evaluation signal comprises a signal having an evaluation frequency that is below the resonant frequency of the loudspeaker, wherein the processing unit is configured for adapting the loudspeaker signal to control the temperature of the voice coil by attenuating the loudspeaker signal in a first frequency band without attenuating the loudspeaker signal in a second frequency band that has a higher frequency than the first frequency band and filtering the input sound signal with a low-pass filter.
2. A sound system as in claim 1 wherein the monitor is configured for monitoring an electric current in the voice coil and, optionally, an electric voltage across the voice coil.
3. A sound system as in claim 1 wherein the evaluation signal comprises a signal having an evaluation frequency.
4. A sound system as in claim 3 wherein the processing unit comprises a spectral analyzer to obtain a frequency component of the monitored response at the evaluation frequency, adapting the loudspeaker signal to control the temperature of the voice coil being in dependency on the frequency component of the monitored response at the evaluation frequency.
5. A sound system as in claim 4 , wherein the spectral analyzer is configured for a Discrete Fourier Transform at the evaluation frequency.
6. A sound system as in claim 1 , the impedance of the loudspeaker and/or temperature of the voice coil being determined from the monitored response, adapting the loudspeaker signal to control the temperature of the voice coil being in dependency on at least one of the determined impedance of the loudspeaker and the temperature of the voice coil respectively.
7. A sound system as in claim 1 wherein the evaluation signal is configured for the loudspeaker to generate one of no and an inaudible sound in response to the evaluation signal.
8. A sound system as in claim 3 , wherein the loudspeaker is configured with a lower frequency bound below which the loudspeaker is configured for generating one of no and an inaudible sound in response to signal components in the loudspeaker signal having a frequency below the lower frequency bound, and wherein the evaluation frequency is below the lower frequency bound.
9. A sound system as in claim 3 , wherein the processing unit comprises a psycho acoustic model for determining a masked frequency, the input sound masking the masked frequency, and wherein the evaluation frequency is configured to be the masked frequency.
10. A sound system as in claim 1 , wherein the processing unit comprises a frequency detector for determining an amplitude of a signal component in the input sound signal of the evaluation frequency, the processing unit being configured for only combining the evaluation signal with the input sound signal if the determined amplitude is below a predetermined threshold.
11. A sound system as in claim 1 , wherein the processing unit is configured for adapting the loudspeaker signal to decrease the temperature of the voice coil in dependency on the monitored response indicating that the temperature of the voice coil is above a predetermined temperature threshold.
12. A method for producing sound, the method comprising
processing an input sound signal to produce a loudspeaker signal, the loudspeaker signal being configured for generating sound through a loudspeaker, the loudspeaker comprising a voice coil for driving the loudspeaker, a temperature of the voice coil depending on the loudspeaker signal,
adapting the loudspeaker signal to control the temperature of the voice coil in dependency on an electric response of the voice coil to the loudspeaker signal by attenuating the loudspeaker signal in a first frequency band without attenuating the loudspeaker signal in a second frequency band that has a higher frequency than the first frequency band and filtering the input sound signal with a low-pass filter,
generating an evaluation signal, and
processing the input sound signal to produce a loudspeaker signal by combining the evaluation signal with the input sound signal, wherein the evaluation signal comprises a signal having an evaluation frequency that is below the resonant frequency of the loudspeaker.
13. A method for obtaining a temperature of a voice coil, the method comprising
processing an input sound signal to produce a loudspeaker signal, the loudspeaker signal being configured for generating sound through a loudspeaker, the loudspeaker comprising a voice coil for driving the loudspeaker, a temperature of the voice coil depending on the loudspeaker signal,
attenuating the loudspeaker signal in a first frequency band without attenuating the loudspeaker signal in a second frequency band that has a higher frequency than the first frequency band and filtering the input sound signal with a low-pass filter;
generating an evaluation signal, processing the input sound signal to produce a loudspeaker signal by combining the evaluation signal with the input sound signal, wherein the evaluation signal comprises a signal having an evaluation frequency that is below the resonant frequency of the loudspeaker, and
determining the temperature of the voice coil in dependency on the monitored response.
14. A non-transitory computer readable storage medium storing a computer program comprising computer program code adapted to perform the steps of claim 12 when the computer program is run on a computer.
15. The sound system of claim 1 , wherein the DC resistance of the loudspeaker being determined from the monitored response, adapting the loudspeaker signal to control the temperature of the voice coil being in dependency on the determined DC resistance of the loudspeaker.
16. The sound system of claim 1 , wherein the monitor is further configured to monitor the electric response of the voice coil to the evaluation signal.
17. The sound system of claim 1 , wherein the processing unit is further configured for adapt the loudspeaker signal to have a predetermined constant energy or amplitude.
18. The sound system of claim 1 , wherein the evaluation signal comprises a single sine wave of a particular evaluation frequency and a fixed amplitude or energy.