Automatic sound level compensator for a sound reproduction device mounted in a vehicle

• US 5,018,205 A
• Filed: 07/11/1990
• Issued: 05/21/1991
• Est. Priority Date: 02/03/1988
• Status: Expired due to Term

• Current Assignee: Pioneer Electronics (USA) Incorporated (Pioneer Corporation)
• Original Assignee: Pioneer Electronics (USA) Incorporated (Pioneer Corporation)
• Inventors: Ito, Masahiko, Takagi, Kazunori, Sato, Shinichi, Yamamoto, Hideo
• Primary Examiner(s): Isen, Forester W.
• Application Number:
  US07/552,364
• Time in Patent Office: 314 Days
• Field of Search: 381/102, 381/98, 381/86, 381/103, 381/57
• US Class Current: 381/86
• CPC Class Codes: H03G 3/32 the control being dependent upon ambient noise level or sound level
• CPC Class Codes: H03G 5/165 Equalizers; Volume or gain control in limited frequency bands
• CPC Class Codes: H03G 9/025 frequency-dependent volume compression or expansion, e.g. multiple-band systems H03G9/10, H03G9/18 take precedence
• CPC Class Codes: H03G 9/18 for tone control and volume expansion or compression

Abstract

In an automatic loudness compensator provided in a sound reproduction device in a vehicle, the sound level is compensated to reproduce a sound source with the high fidelity intended by the producer of the source of sound. The level of sound frequency-pressure is increased or decreased relative to a middle range of sound frequency at a sound level lower or higher than a reference sound level, respectively. The level of sound frequency-pressure is also adjusted based on the noise produced by the movement of the vehicle and on the acoustic characteristic of the passenger compartment of the vehicle.

Claims

1. A sound reproduction device including an automatic loudness compensator for compensating a sound level of an audio signal, comprising;

means for increasing a first level of sound pressure of said audio signal in a first range of sound frequency relative to a second level of sound pressure in a middle range of sound frequency when a sound level of said audio signal is lower than a reference sound level; and

means for decreasing said first level of sound pressure relative to said second level of sound pressure in said middle range of sound frequency when said sound level of said audio signal is higher than said reference sound level;

wherein said sound reproduction device is mounted in a vehicle; and

further comprising;

means for adjusting said first level of sound pressure relative to said second level of sound pressure based on a noise produced by movement of said vehicle.

2. A sound reproduction device including an automatic loudness compensator for compensating a sound level of an audio signal, comprising:

means for increasing a first level of sound pressure of said audio signal in a first range of sound frequency relative to a second level of sound pressure in a middle range of sound frequency when a sound level of said audio signal is lower than a reference sound level; and

means for decreasing said first level of sound pressure relative to said second level of sound pressure in said middle range of sound frequency when said sound level of said audio signal is higher than said reference sound level;

wherein said sound reproduction device is mounted in a vehicle; and

further comprising;

means for adjusting said first level of sound pressure relative to said second level of sound pressure based on an acoustic characteristic of a passenger compartment of said vehicle.

3. A sound reproduction device including an automatic loudness compensator for compensating a sound level of an audio signal, comprising:

means for increasing a first level of sound pressure of said audio signal in a first range of sound frequency relative to a second level of sound pressure in a middle range of sound frequency when a sound level of said audio signal is lower than a reference sound level;

means for decreasing said first level of sound pressure relative to said second level of sound pressure in said middle range of sound frequency when said sound level of said audio signal is higher than said reference sound level;

first filter means for extracting a middle-frequency sound range component from said audio signal;

second filter means for extracting a low-frequency and a high-frequency sound range component from said audio signal;

means for logarithmically compressing the output of said second filter means;

means for limiting the level of the output of said logarithmic compressing means; and

means for adding the output of said level limiting means to the output of said first filter.

4. An automatic loudness compensator as in claim 3, further comprising:

a high-pass filter having an input connected to said input audio signal and an output connected to the input of said second filter means.

5. A sound reproduction device including an automatic loudness compensator for compensating a sound level of an audio signal, comprising:

means for increasing a first level of sound pressure of said audio signal in a first range of sound frequency relative to a second level of sound pressure in a middle range of sound frequency when a sound level of said audio signal is lower than a reference sound level;

means for decreasing said first level of sound pressure relative to said second level of sound pressure in said middle range of sound frequency when said sound level of said audio signal is higher than said reference sound level;

first filter means for extracting a middle-frequency sound range component from said audio signal;

second filter means for extracting a low-frequency sound range component from said audio signal;

third filter means for extracting a high-frequency sound range component from said audio signal;

first logarithmic compression means for logarithmically compressing the output of said second filter means;

second logarithmic compression means for logarithmically compressing the output of said third filter means;

first limiting means for limiting the level of the output of said first logarithmic compression means;

second limiting mans for limiting the level of the output of said second logarithmic compression means; and

means for adding the outputs of said first limiting means, said second limiting means, and said first filter means

6. A sound reproduction device including an automatic loudness compensator for compensating a sound level of an audio signal, comprising;

means for increasing a first level of sound pressure of said audio signal in a first range of sound frequency relative to a second level of sound pressure in a middle range of sound frequency when a sound level of said audio signal is lower than a reference sound level;

means for decreasing said first level of sound pressure relative to said second level of sound pressure in said middle range of sound frequency when said sound level of said audio signal is higher than said reference sound level;

first filter means for extracting a middle-frequency sound range component from said audio signal in a first channel;

second filter means for extracting a high-frequency sound range component from said audio signal in said first channel;

third filter means for extracting a middle-frequency sound range component from said audio signal in a second channel;

fourth filter means for extracting a high-frequency sound range component from said audio signal in said second channel;

fifth filter means for extracting a low-frequency sound range component from a combined input signal comprising said audio signals in said first and second channels;

first logarithmic compression means for logarithmically compressing the output of said second filter means;

second logarithmic compression means for logarithmically compressing the output of said fourth filter means;

third logarithmic compression means for logarithmically compressing the output of said fifth filter means;

first limiting means for limiting the level of the output of said third logarithmic compression means;

first adding means for adding the outputs of said first filter means, said first logarithmic compression means and said first limiting means to form an audio output signal in said first channel; and

second adding means for adding the outputs of said third filter means, said second logarithmic compression means, and said first limiting means to form an audio output signal in said second channel.

7. An automatic loudness compensator as in claim 6, further comprising:

second limiting means for limiting the level of the output of said first logarithmic compression means, the output of said second limiting means being provided to said first adding means in place of the output of said first logarithmic compression means; and

third limiting means for limiting the level of the output of said second logarithmic compression means, the output of said third limiting means being provided to said second adding means in place of the output of said second logarithmic compression means.