Abstract: A resonant frequency characteristic in a resonant space is detected, based on a base amplitude frequency characteristic obtained by outputting a sound wave of a specified measurement signal from a speaker 13 disposed in a sound space 40 and by receiving the sound wave in a microphone 14 disposed in the sound space 40, a first amplitude frequency characteristic obtained by outputting, from the speaker 13, a sound wave of the measurement signal and a signal output from the microphone 14 and by receiving the sound wave in the microphone 14, and a second amplitude frequency characteristic obtained by outputting, from the speaker 13, a sound wave of the measurement signal and a phase inverted signal obtain by inverting a phase of the signal output from the microphone 14 and by receiving the sound wave in the microphone 14.

Abstract: Resonant frequencies f2 and f3 detected in a resonant space are determined as center frequencies of a dip. Based on measurement values at a speaker and a microphone in the resonant space, a basic amplitude frequency characteristic Ca and a target amplitude frequency characteristic Cd are found. A smoothness degree on a frequency axis is larger in the target amplitude frequency characteristic Cd than the basic amplitude frequency characteristic Ca. A damping level and quality factor of the dip are determined based on a difference between the basic amplitude frequency characteristic Ca and the target amplitude frequency characteristic Cd in the center frequencies f2 and f3 of the dip and frequencies near the center frequencies.

Abstract: A howling margin measuring device 20 comprises processing means 28 composed of gain controlling means 21 and a compressor 22 which are connected in series and controlling means 23. The gain controlling means 21 outputs an input sound signal after giving a gain thereto. If the level of a sound signal input to the compressor 22 is equal to or higher than a threshold level, the compressor 22 outputs the sound signal after compressing it with a specified ratio. The controlling means 23 is capable of controlling the gain of the gain controlling means 21 and reading the compression level of the compressor 22.

Abstract: A device 1 for measuring a propagation time of a sound wave comprises a sound source means 11 and a calculation means 12. The sound source means 11 outputs a time stretched pulse as a sound source signal input to a speaker 3. The calculation means 12 calculates a cross-correlation function of the time stretched pulse and the sound signal which is output from the speaker 3 and is received in a microphone 4. Based on the cross-correlation function, the propagation time of the sound wave between the speaker 3 and the microphone 4 is found.

Abstract: A resonant frequency characteristic in a resonant space is detected, based on a base amplitude frequency characteristic obtained by outputting a sound wave of a specified measurement signal from a speaker 13 disposed in a round space 40 and by receiving the sound wave in a microphone 14 disposed in the round space 40, a first amplitude frequency characteristic obtained by outputting, from the speaker 13, a sound wave of the measurement signal and a signal output from the microphone 14 and by receiving the sound wave in the microphone 14, and a second amplitude frequency characteristic obtained by outputting, from the speaker 13, a sound wave of the measurement signal and a phase inverted signal obtain by inverting a phase of the signal output from the microphone 14 and by receiving the sound wave in the microphone 14. The second delay time is different from the first delay time.

Abstract: A device for detecting a resonant frequency comprises a sound source, a switch, a mixer, and a sound meter. The switch and mixer are capable of switching between a first state in which the switch and mixer output a measurement signal and a second state in which the switch and mixer output a synthesized signal containing the measurement signal and the signal output from a microphone. The device detects the resonant frequency based on comparison between the first amplitude frequency characteristic measured in the first state and the second amplitude frequency characteristic measured in the second state.

Abstract: A howling margin measuring device 20 comprises processing means 28 composed of gain controlling means 21 and a compressor 22 which are connected in series and controlling means 23. The gain controlling means 21 outputs an input sound signal after giving a gain thereto. If the level of a sound signal input to the compressor 22 is equal to or higher than a threshold level, the compressor 22 outputs the sound signal after compressing it with a specified ratio. The controlling means 23 is capable of controlling the gain of the gain controlling means 21 and reading the compression level of the compressor 22.

Abstract: Resonant frequencies f2 and f3 detected in a resonant space are determined as center frequencies of a dip. Based on measurement values at a speaker and a microphone in the resonant space, a basic amplitude frequency characteristic Ca and a target amplitude frequency characteristic Cd are found. A smoothness degree on a frequency axis is larger in the target amplitude frequency characteristic Cd than the basic amplitude frequency characteristic Ca. A damping level and quality factor of the dip are determined based on a difference between the basic amplitude frequency characteristic Ca and the target amplitude frequency characteristic Cd in the center frequencies f2 and f3 of the dip and frequencies near the center frequencies.

Abstract: A device 1 for measuring a propagation time of a sound wave comprises a sound source means 11 and a calculation means 12. The sound source means 11 outputs a time stretched pulse as a sound source signal input to a speaker 3. The calculation means 12 calculates a cross-correlation function of the time stretched pulse and the sound signal which is output from the speaker 3 and is received in a microphone 4. Based on the cross-correlation function, the propagation time of the sound wave between the speaker 3 and the microphone 4 is found.

Abstract: A device 20 for detecting a resonant frequency comprises a sound source means 21, a signal synthesization switching means 26 and 27, and a measuring means 25. The signal synthesization switching means 26 and 27 are capable of switching between a first state in which the signal synthesization switching means 26 and 27 outputs a measurement signal and a second state in which the signal synthesization switching means 26 and 27 outputs a synthesized signal containing the measurement signal and the signal output from a microphone 14. The device 20 detects the resonant frequency based on comparison between the first amplitude frequency characteristic measured in the first state and the second amplitude frequency characteristic measured in the second state.