Masking sound generating apparatus, masking system, masking sound generating method, and program

A masking system comprising:

• a microphone that collects a sound and inputs an audio signal representing the collected sound;
• a band dividing part that receives the audio signal provided from the microphone, then divides the audio signal into a plurality of frequency bands, and generates a plurality of band signals belonging respectively to the plurality of the frequency bands;
• an envelope signal generating part that generates a plurality of envelope signals representing respective envelopes of the plurality of the band signals generated by the band dividing part;
• a signal converting part that applies to each of the plurality of the envelope signals generated by the envelope signal generating part a signal conversion process so as to randomize sections of the envelope signal which are greater than a first threshold and less than a second threshold which is greater than the first threshold, and outputs the plurality of the envelope signals each applied with the signal conversion process;
• a multiplying part that multiplies each envelope signal outputted from the signal converting part by a signal belonging to a frequency band same as that of each envelope signal, and outputs the plurality of the envelope signals multiplied by the signals as individual band masking signals corresponding to the respective frequency bands;
• an adding part that adds the individual band masking signals output by the multiplying part and outputs a masking sound signal as a result of the addition;
• and
• a speaker that outputs a sound according to the masking sound signal output from the adding part.

A masking system comprising:

• a non-transitory recording medium that records an audio signal;
• a reading part that reads out the audio signal from the recording medium;
• a band dividing part that receives the audio signal provided from the reading part, then divides the audio signal into a plurality of frequency bands, and generates a plurality of band signals belonging respectively to the plurality of the frequency bands;
• an envelope signal generating part that generates a plurality of envelope signals representing respective envelopes of the plurality of the band signals generated by the band dividing part;
• a signal converting part that applies to each of the plurality of the envelope signals generated by the envelope signal generating part a signal conversion process so as to randomize sections of the envelope signal which are greater than a first threshold and less than a second threshold which is greater than the first threshold, and outputs the plurality of the envelope signals each applied with the signal conversion process;
• a multiplying part that multiplies each envelope signal outputted from the signal converting part by a signal belonging to a frequency band same as that of each envelope signal, and outputs the plurality of the envelope signals multiplied by the signals as individual band masking signals corresponding to the respective frequency bands;
• an adding part that adds the individual band masking signals output by the multiplying part and outputs a masking sound signal as a result of the addition;
• and
• a speaker that outputs a sound according to the masking sound signal output from the adding part.

A masking sound generating method comprising:

• a band dividing process of dividing an audio signal into a plurality of frequency bands, and generating a plurality of band signals belonging respectively to the plurality of the frequency bands;
• an envelope signal generating process of generating a plurality of envelope signals representing respective envelopes of the plurality of the band signals generated by the band dividing process;
• a signal converting process of applying to each of the plurality of the envelope signals generated by the envelope signal generating process a signal conversion so as to randomize sections of the envelope signal which are greater than a first threshold and less than a second threshold which is greater than the first threshold, and outputting the plurality of the envelope signals each applied with the signal conversion;
• a multiplying process of multiplying each of the plurality of the envelope signals applied with the signal conversion by a noise signal, and outputting the plurality of the envelope signals multiplied by the noise signal as individual band masking signals corresponding to the respective frequency bands;
• and
• an adding process of adding the individual band masking signals output by the multiplying process, and outputting a masking sound signal as a result of the addition.

A non-transitory machine readable medium for use in a computer, containing program instructions executable by the computer to perform:

• a band dividing process of dividing an audio signal into a plurality of frequency bands, and generating a plurality of band signals belonging respectively to the plurality of the frequency bands;
• an envelope signal generating process of generating a plurality of envelope signals representing respective envelopes of the plurality of the band signals generated by the band dividing process;
• a signal converting process of applying to each of the plurality of the envelope signals generated by the envelope signal generating process a signal conversion so as to randomize sections of the envelope signal which are greater than a first threshold and less than a second threshold which is greater than the first threshold, and outputting the plurality of the envelope signals each applied with the signal conversion;
• a multiplying process of multiplying each of the plurality of the envelope signals applied with the signal conversion by a signal belonging to a frequency band same as that of each envelope signal, and outputting the plurality of the envelope signals multiplied by the noise signal as individual band masking signals corresponding to the respective frequency bands;
• and
• an adding process of adding the individual band masking signals output by the multiplying process, and outputting a masking sound signal as a result of the addition.