Electrical audio signal processing systems and devices – Headphone circuits
Reexamination Certificate
1998-04-23
2001-01-23
Harvey, Minsun Oh (Department: 2747)
Electrical audio signal processing systems and devices
Headphone circuits
C381S309000
Reexamination Certificate
active
06178247
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a headphone apparatus, and in particular, to a headphone apparatus which has an excellent extra-head localization effect of its acoustic image (imaginary sound source).
BACKGROUND ART
Conventionally, headphone apparatuses have had the problem that they give an unnatural feeling as well as a feeling of fatigue to the listener because an acoustic image produced by audio signals outputted from left and right headphones are formed inside the head or near both ears which is different from the case where the audio signals are heard from speakers.
Accordingly, a variety of means have been proposed lately for the purpose of enabling the extra-head localization of the acoustic image. For example, a headphone apparatus disclosed in the document of Japanese Patent Laid-Open Publication No. HEI 3-250900 enables extra-head localization by taking reflection sounds which reach the ears through reflection on walls and the like into consideration, in addition to sounds which reach the ears directly.
However, even the aforementioned headphone apparatus still has an unnatural feeling in comparison with the case where sounds are heard from speakers or the like, and it has a problem particularly in the extra-head localization in the depthwise direction and the vertical direction. This is also apparently disadvantageous in considering the fact that we can obtain directivity of a sound even when listening to the sound from speakers in an anechoic room.
In view of the above, the present inventor has discovered that a reflection sound on the shoulder is an important factor in determining the directivity of a sound and obtaining an appropriate extra-head localization by taking into consideration how much the reflection sound is delayed on the shoulder relative to a direct sound.
SUMMARY OF THE INVENTION
That is, according to the present invention, there is provided a headphone apparatus comprising: a first direct sound generating means for generating a first direct sound audio signal corresponding to a sound which travels from an imaginary sound source and directly reaches one ear by delaying an input audio signal; a second direct sound generating means for generating a second direct sound audio signal corresponding to a sound which travels from the imaginary sound source and directly reaches the other ear by delaying the input audio signal; a first reflection sound generating means for generating a first reflection sound audio signal corresponding to a sound which travels from the imaginary sound source, reaches a shoulder and thereafter reaches the one ear through reflection by delaying the input audio signal; a second reflection sound generating means for generating a second reflection sound audio signal corresponding to a sound which travels from the imaginary sound source, reaches a shoulder and thereafter reaches the other ear through reflection by delaying the input audio signal; a first adding means for adding the first direct sound audio signal to the first reflection sound audio signal, thereby generating a first combined sound audio signal; a second adding means for adding the second direct sound audio signal to the second reflection sound audio signal, thereby generating a second combined sound audio signal; and headphones for reproducing the first combined sound audio signal from the first adding means and the second combined sound audio signal from the second adding means independently at left and right ears, respectively.
The aforementioned first and second direct sound generating means delay the input audio signal to make the direct sound audio signal corresponding to the sound which travels from the imaginary sound source and directly reaches the ears. When distances from the imaginary sound source to the left and right ears differ from each other, the phase of the audio signal to be outputted is shifted between the first and second direct sound generating means. With this arrangement, the position of the imaginary sound source can be localized in a lateral direction. The first and second reflection sound generating means delay the input audio signal to make the reflection sound audio signal corresponding to the sound which travels from the imaginary sound source, impinges once on the shoulder and thereafter reaches the ears. The reflection sound audio signals are respectively obtained by shifting the phases of the corresponding direct sound audio signals. The adding means combine the direct sound audio signals with the reflection sound audio signals for the left and right ears, and the resulting sounds are reproduced independently at left and right headphones. This arrangement enables the localization of the position of the imaginary sound source in a depthwise direction, thereby allowing sounds to have a greater expanse in the depthwise direction than with the prior art headphone apparatus.
It is acceptable to combine the generating means as one unit and provide a plurality of the units according to the number of imaginary sound sources. According to this arrangement, each of the aforementioned units delays the input audio signal so that audio signals corresponding to the direct sound and the reflection sound from the corresponding imaginary sound source can be obtained. Therefore, these audio signals are combined and reproduced by the headphone, and consequently the obtained imaginary sound sources are localized in a plurality of places, thereby allowing a concert-hall presence to be appreciated similar to that of, for example, a live performance of an orchestra.
It is acceptable to make the phase shift of the reflection sound audio signals adjustable relative to the direct sound audio signals. According to this arrangement, when the phase shift of the reflection sound audio signals relative to the direct sound audio signals is adjusted by changing the delay time, the obtained imaginary sound source can be localized not only in the lateral and depthwise directions, but also in a vertical direction.
It is acceptable to provide a sound pressure adjusting means for suppressing a sound pressure level of the audio signal generated by each of the direct sound generating means as the phase shift relative to the input audio signal increases between the direct sound generating means and the adding means. The sound pressure adjusting means may suppress the sound pressure level on a treble region side of the audio signal whose sound pressure level has been suppressed further than that on a bass region side. According to this arrangement, the aforementioned sound pressure adjusting means clarifies the direction of the imaginary sound source by suppressing the sound pressure level, or in particular, the sound pressure level on the treble region side of the generating means when a long delay time is set.
It is acceptable to provide a first diffraction sound generating means for generating a first diffraction sound audio signal corresponding to a sound which travels from a sound source and reaches the right ear through diffraction on a face by delaying the input audio signal and a second diffraction sound generating means for generating a second diffraction sound audio signal corresponding to a sound which travels from a sound source and reaches the left ear through diffraction on the face by delaying the input audio signal, make the first adding means add the first diffraction sound audio signal to the first direct sound audio signal and the first reflection sound audio signal and make the second adding means adding the second diffraction sound audio signal to the second direct sound audio signal and the second reflection sound audio signal. According to this arrangement, a more appropriate sound source direction can be obtained by taking the diffraction sound component on the face into consideration.
REFERENCES:
patent: 4136260 (1979-01-01), Asahi
patent: 4589128 (1986-05-01), Pfleiderer
patent: 52-11002 (1977-01-01), None
patent: 3-250900 (1991-11-01), None
Harvey Minsun Oh
Wenderoth , Lind & Ponack, L.L.P.
Yugengaisha Ito Denkitekkousyo
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