Abstract: An input audio signal is AD converted into digital signals which are processed by a central processing unit (CPU) in which Fast Fourier Transform (FFT) operation and power spectrum calculation are effected. As a result power spectrum data is obtained, and then position determination is effected to determine the position of each bar of a bar graph to be displayed on a display unit screen, according to the power level at different frequencies within the spectrum of the audio signal. Pattern data is then produced in correspondence with the determined position, and output data from the CPU is fed via a video display processor to a video RAM, thereby displaying the spectrum by way of a predetermined pattern of a bar graph on the screen. In order to reduce the number of digital data used in FFT operation the input audio signal may be divided into a plurality of different frequency bands so that different sampling frequencies are used for AD conversion of signals of respective bands.

Abstract: In a circuit arrangement for automatically correcting frequency response so as to set a desired frequency response in view of a frequency response of a sound field, a frequency response control circuit is improved such that precise level control at a number of bands is effected with a simple structure. A microcomputer is used to determine the difference between a desired frequency response curve and a frequency response curve obtained by measuring the sound pressure level in a sound field, to which pink noise or the like is emitted through the frequency response control circuit, so as to produce a control signal used in the frequency response control circuit to give a desired frequency response to an audio signal.

Abstract: An input audio signal is analog-to-digital (AD) converted into digital data which is processed by a central processing unit (CPU) for determining pitch of each sound by effecting Fast Fourier Transform (FET) operation and power spectrum calculation. The determination of the sound pitch is effected twice in sequence, and by using frequency and level data resulted from two consecutive determinations, the time length of the sound is detected. After the pitch and the time length are determined, data indicative of a given musical note pattern is produced so that a musical note indicative of time value is indicated at an appropriate position on a staff displayed on a screen of a display unit. Such data from the CPU is fed via a video display processor to a video RAM to be stored therein where the video display processor produces a video signal fed to the display unit in turn.

Abstract: An input audio signal is AD converted into digital data which is processed by a central processing unit (CPU) in which Fast Fourier Transform (FFT) operation and power spectrum calculation are effected. Furthermore, spectrum data obtained in this way is processed to obtain a fundamental tone to determine the pitch of each sound of the input audio signal. After the pitch is determined, data indicative of a given pattern is produced so that a musical note is indicated at an appropriate position on a staff displayed on a screen of a display unit. Such data from the CPU is fed via a video display processor to a video RAM to be stored therein where the video display processor produces a video signal fed to the display unit in turn. Since the fundamental tone does not necessarily have the highest level within the spectrum of the input audio signal, various ways for accurate determination of the pitch are used.

Abstract: A test signal is recorded on a magnetic tape prior to the recording of audio signals and reproduced to allow detection of an average value of the magnitude of the reproduced test signal. A drop-out in the reproduced signal is detected if it occurs during the process of deriving the average value. If the drop-out is not detected, a difference between the average value and a reference value is detected to adjust the signal level of the recorded test signal so that the difference reduces substantially to zero. If a drop-out is detected the average value is renewed by repeating the process of recording and reproducing the test signal.