Pioneer Electronic Corporation

Shuichi Mori

Hisashi Kihara

Shinjiro Kato

Fumio Tamura

Akio Tokumo

Takashi Miyake

Yoshikatsu Ikata

Nobuo Utsugi

Junichi Fuse

Takeshi Sato

Toshikazu Yoshimi

Hideo Yamamoto

Shunsuke Ishimitsu

Masayuki Kato

Kazunori Takagi

Takashi Sakakibara

Akira Kanagawa

Yasumasa Fukatsu

Atsushi Makino

Shinya Honjo

A digital graphic equalizer for obtaining a boost characteristic and an attenuation characteristic using band pass filters, each constituted by a digital filter, and an adder. For a boost characteristic, an input signal is supplied to first band pass filters and resultant filtered signals and the input signal are added by a first adder. For an attenuation characteristic, the output signal of a second adder is fed back to second band pass filters and resultant filtered signals and the input signal are added by a second adder.

Digital graphic equalizer

A signal processing circuit for an audio apparatus has a variable gain amplifier whose gain is varied in accordance with a gain controlling signal supplied thereto. The signal processing circuit comprises a gain setting section having a plurality of tables of input-output characteristics according to a level of loudness selected by a user. The characteristics being for the variable gain amplifier. A table selecting section selects a corresponding one of the plurality of input-output characteristics in accordance with the selected level of loudness. The table selecting section supplies the corresponding input-output characteristic to the variable gain amplifier so as to set the variable gain amplifier for a gain corresponding to the input-output characteristic.

Signal processing circuit for audio apparatus

A signal processing circuit in an audio device includes a variable gain control section for providing a variable amplification gain to an input signal in response to a gain control signal, an input signal level detecting section for detecting a level of the input signal and for generating a corresponding detection signal, and a time constant setting section for storing a plurality of time constant tables. Each one of the plurality of time constant tables includes a set of input signal delay characteristics corresponding to a predetermined level of the input signal. A time constant selecting section selects one of the plurality of time constant tables in the time constant setting section in response to the detection signal. The gain control signal is determined by the selected one of the plurality of time constant tables and the amplification gain of the variable gain control section is varied according to the selected one of the plurality of time constant tables.

Signal processing circuit in an audio device

A tone control apparatus for a sound system processing audio signals of front and rear channels. By providing front and rear tone control means for independently effecting the tone control in both of the front and rear channels, it is possible to prevent the generation of distortions in the front acoustic output when the control for raising the rear bass level is effected. Also, a tone control balance between the front and rear channels in a vehicle cabin, for example, can be set appropriately.

Tone control apparatus for front and rear channels

Tuner for receiving a plurality of receiving frequencies and audio system having a plurality of audio components, characterized by the provision of a device for generating a designation command for selectively designating a program source such as a broadcast station at the receiving frequency of the tuner or an audio component, and an equalizer for adjusting the audio signal from the selected program source to have a frequency characteristic according to the program source designated by the designation command. By this provision, the need of operating tone controls at each time of the change of program source is obviated, so that the readiness of operation is improved.

Tuner with selective equalization of different program sources

Disclosed herein is a digital audio signal processing apparatus of a type wherein a graphic equalizer including a plurality of filters connected in series to one another is subjected to arithmetic operation processing to be defined to thereby output the result of its processing as data therefrom. When a change-over command is generated, one filter out of the plurality of filters except for filters positioned at both ends is supplied to one of two output terminals with output data of a filter immediately before said one filter, the stored data is applied to the input of a filter immediately after said one filter and output data of a final filter is applied to the other of said two output terminals so as to define two graphic equalizers. Thus, where it is desired to carry out a change in the mode from arithmetic operation processing which defines a graphic equalizer comprising a plurality of bands to arithmetic operation processing which defines two-separated graphic equalizers comprising a plurality of bands or to the contrary, where it is desired to carry out a change in the mode contrary to the mode referred to above, the change in the arithmetic operation processing can be completed in a relatively short time.

Digital audio signal processing apparatus

AN on-board vehicle automatic sound volume adjusting apparatus which adjusts the level of an input audio signal in accordance with the difference between the input audio signal level and the running noise level inside the vehicle and which compresses the input audio signal in terms of amplitude according to the level difference. The apparatus inhibits the masking of the minimum component in the reproduced sound volume, and prevents the maximum component therein from becoming excessive when the running noise level is raised.

On-board vehicle automatic sound volume adjusting apparatus

A sound field correcting device provides for a natural acoustic localization of the outputs of right and left channels of an acoustic sound source. At least one of right and left channel audio signals is delayed to create a phase difference between the right and left channel audio signals, and to thus dislocate a sound in such a way that a listener not positioned equidistant between right and left channel sound sources may perceive the two channels equally.

Device for correcting a sound field in a narrow space

An automatic sound volume controller for use with audio equipment mounted on a vehicle adapted that the level of an input audio signal and that of the noises coming inside the cabin in running state are detected, and the difference therebetween is obtained. By use of different gain levels reflecting the level difference, a direct sound signal and an effect sound signal are individually amplified for synthesis. This makes it possible to prevent the added effect sounds from being masked by the running noises because the level of the effect sound signal varies with the noises. As a result, the reproduced sounds supplemented by the effect sounds can be heard clearly while the vehicle is running. With the vehicle in stationary state, the effect sounds are kept from getting excessive, protecting the vehicle passengers from the unpleasant sensation conventionally associated with the apparatus of this kind.

Automatic sound volume controller

Frequency characteristic setting circuitry for an amplifier generates frequency band data groups using a plurality of characteristic pattern data groups stored in a memory. Each of the frequency band data groups is made by making each item of data of a characteristic pattern data group retrieved from among a plurality of characteristic pattern data groups stored in the memory correspond to each frequency in a designated frequency band. The data groups generated for a plurality of frequency bands are combined together and the equalizing characteristic of the amplifier is controlled according to a characteristic pattern data group obtained by the combination.

Frequency characteristic setting circuitry for an amplifier

In an ALC circuit for automatically performing an amplitude compression control operation according to the output level of a low frequency amplifier circuit, the output level of the amplifier circuit is subjected to amplitude compression according to the level of a control signal which is outputted in correspondence to the output level of the amplifier circuit. The differentiation time constant of a differentiating circuit (or cutoff frequency of a high pass filter) provided on the output side of the amplifier circuit is controlled according to the level of the control signal to control the cutoff frequency for the frequency band subjected to amplitude compression.

Automatic level control circuit

A recording medium player apparatus including an open/close body which is disposed so as to openably cover a recording medium insertion slot formed in the front surface portion of a housing. The open/close body has an operation portion for controlling the operation of a play mechanism. The apparatus further includes a support member for pivotally supporting at a free end thereof the open/close body. A spring member constitutes a first driving mechanism for pivoting the support member. The spring member, a gear disposed on the support member, and a pair of fan-like gears which mesh with the gear disposed on the support member constitute a second driving mechanism for pivoting the open/close body relative to the support member in synchronism with the pivotal movement of the support member. This configuration enables the pivotal portion of the open/close body to be disposed at a rear surface portion of the open/close such that the pivotal portion is covered by the front panel portion of the open/close body when the open/close body is in a closed position.

Recording medium player apparatus

A limiter circuit divides the output of a low frequency amplifier into two parts which are respectively high pass filtered, and low frequency amplitude limited. The two parts may be recombined to form an audio output which is freed from clipping distortion at the low end, while the high end is increased. The invention is especially suited for environments such as automobiles, where the ambient noise level may be high.

Limiter circuit

A headrest-mounted acoustic device including at least a speaker mounted on the right or left side of a headrest provided on a seat, a cover mounted in the sound radiating direction of the speaker, and a sound radiating portion communicating with a chamber provided behind the cover and having an area much smaller than that which is defined by the diameter of the speaker, so that sounds from the speaker are radiated from the sound radiating part through the chamber.

Headrest-mounted acoustic device

An automatic sound volume control device for use in a device such as a radio or tape player used in a high ambient noise environment. The noise and sound signal levels above predetermined reference levels are detected and a control signal is produced having a level determined in accordance with the output signals so produced. The amplification gain of the sound signal is set by this control signal. Several different ways of producing the control signal are described, each of which has particular advantages in different situations and for different types of reproduced sound.

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Kawagoe, Japan

Shuichi Mori