Audio processing device for a ceiling reflection type speaker
To resolve a problem that a listener feels that sense of localization and sense of connecting with the other channels are lost in case that the listener listens to an audio that is output from a ceiling reflection type speaker in an audio processing device that outputs an analog audio signal to speakers including the ceiling reflection type speaker that makes the audio reflect at a ceiling. A DSP 5 performs low-pass filter processing that extracts low frequency component from a digital audio signal, high-pass filter processing that extracts high frequency component from the digital audio signal, delay processing that delays the low frequency component of the digital audio signal that is extracted by the low-pass filter processing, and composition processing that composes the low frequency component of the digital audio signal that is delayed by the delay processing and the high frequency component of the digital audio signal that is extracted by the high-pass filter processing as audio signal processing.
1. An audio processing device that outputs an analog audio signal to speakers including at least one ceiling reflection type speaker that reproduces an audio toward a ceiling, and at least one non-ceiling reflection type speaker, comprising:
a digital signal processor that performs audio signal processing on a digital audio signal, the digital audio signal including at least one non-ceiling reflection type speaker signal and at least one ceiling reflection type speaker signal; and
a digital to analog (D/A) converter that converts the digital audio signal, including the at least one non-ceiling reflection type speaker signal and the at least one ceiling reflection type speaker signal, which has been processed by the digital signal processor into an analog audio signal,
wherein only for the at least one ceiling reflection type speaker the digital signal processor performs low-pass filtering that extracts a low frequency component from the digital audio signal, high-pass filtering that extracts a high frequency component from the digital audio signal, delay processing that delays only the low frequency component of the digital audio signal that is extracted by the low-pass filtering, and composition processing that composes the low frequency component of the digital audio signal that is delayed by the delay processing and the high frequency component of the digital audio signal that is extracted by the high-pass filtering as the audio signal processing;
wherein the digital signal processor delays only the low frequency component of the digital audio signal with a time difference between time that an audio arrives at a listener after reflecting at the ceiling from the at least one ceiling reflection type speaker and time that an audio arrives from the at least one ceiling reflection type speaker at the listener directly in the delay processing, wherein the at least one non-ceiling reflection type speaker is undelayed relative to the at least one ceiling reflection type speaker.
2. The audio processing device according to claim 1 , wherein the digital signal processor performs calculation of (Lr−Ld)/Vs so as to calculate the time difference wherein a distance of a reflected route that the audio arrives at the listener after reflecting at the ceiling from the ceiling reflection type speaker is “Lr”, the distance of a direct route that the audio arrives from the ceiling reflection type speaker at the listener directly is “Ld”, and sound speed is “Vs”.
3. The audio processing device according to claim 2 , wherein the digital signal processor measures the distance of the direct route “Ld” by sound field correction.
4. The audio processing device according to claim 2 , wherein the digital signal processor performs calculation of 2×(Lc 2 +(Ld/2) 2 )) 1/2 so as to calculate the distance of the reflected route “Lr” wherein the shortest distance from the ceiling reflection type speaker to the ceiling is “Lc”.
5. The audio processing device according to claim 4 , further comprising: a controller that receives setting of the distance to the ceiling “Lc”.
6. The audio processing device according to claim 1 , wherein the digital audio processor extracts the low frequency component not more than 2.5 kHz from the digital audio signal in the low-pass filtering and extracts the high frequency component not less than 2.5 kHz from the digital audio signal in the high-pass filtering.
7. The audio processing device of claim 1 , wherein the high frequency component of the digital audio signal, which is composed with the low frequency component of the digital audio signal, is undelayed relative to the low frequency component of the digital audio signal.