| 摘要 |
PURPOSE:To effectively suppress periodic noises picked up by microphone by subtracting periodic noises of a rotating body from the sound signals outputted from the microphone. CONSTITUTION:Sound signals are sampled at a sampling frequency which is an interger multiple frequency of the rotation frequency of a rotating drum and inputted to an averaging circuit 5. On the other hand, the data, which are written from a memory circuit 6 with the timing synchronized to the rotating period of the rotating drum and are written equivalent to one period prior to the rotating period of the drum, are read and inputted to the circuit 5. At the circuit 5, the averaged signals, which are the average of digital sound signals and the data read from the circuit 6, are obtained and are written into the addresses of the circuit 6. By this averaging process, the periodic noises, which are produced by mixing the sound signals picked up by a microphone 1 and the noises generated by the rotating drum, are extracted. The extracted signals are transmitted to a subtracting circuit 10 and subtracted. |
