Abstract: The present invention relates to an inexpensive environmental noise reduction type inner earphone which allows a user to listen music with high quality of sound and with a small volume under noisy environments making noise of 86 dB or more such as in aircraft seats, subways, trains and so on, and particularly which is capable of blocking a high level of environmental noise and regeneration sound passing through the inner earphone by filling a space formed between an ear and the inner earphone with a sound insulation element made of porous soft plastic. The earphone includes a frequency characteristic correction circuit which serves to correct a sound insulation characteristic of the sound insulation element between a voice coil of the earphone and a plug of the earphone and includes a resistor and a capacitor.

Abstract: The present invention relates to low sound reproduction of a compact speaker, a degree of freedom of design for the low sound reproduction, chattering noise of structures of electronic apparatuses due to powerful low sound reproduction, chattering noise of structures near a car speaker due to powerful low sound reproduction, leakage of sound out of a vehicle, and an exterior design of unattractive passive radiators. Specifically, a bottom-raised box part is installed in an enclosure to adjust a volume of the enclosure. A plurality of pairs of passive radiators having different resonance conditions is installed. An external enclosure is installed in the outside of the speaker system including a driver, passive radiators and an enclosure. Signal processing is performed to {suppress a gain at a resonance point of the lowest frequency band providing the maximal vibration of the driver} and {emphasize a gain at a resonance point of the lowest frequency band providing the minimal vibration of the driver}.

Abstract: An audio signal waveform emphasis processing device performs even-order integration on an input audio signal using one or a plurality of double integrators and even-order differentiation on the input audio signal using one or a plurality of double differentiators so as to obtain even-order integrated signal and even-order differentiated signal, and adds the even-order integrated signal and the even-order differentiated signal to the input audio signal in the same phase or reverse-phase with the input audio signal, whereby sound quality of audio signal in audio equipment is greatly improved by obtaining a desired frequency-gain characteristic without destroying the mutual phase relationship between, in particular, the middle frequency range vs. high frequency range and the middle frequency range vs. low frequency range frequency components close to the middle frequency range of an input audio signal.