2 ch sound field reproduction systems
OSS 2 ch sound field reproduction system
The Ortho-Stereophonic System (OSS) is a system designed to reproduce the actual recording sound space in an anechoic room or listening room using two speakers. This system is capable of reproducing audible omnidirectional sounds that are generally difficult to achieve with normal stereo playback, including "up/down" and "front/back," as if the listener were actually situated in the space (virtual reality).*
Humans are said to hear sounds from various directions based on differences in sound pressure levels reaching ears, phase differences, and other factors.
Based on this principle, the OSS uses a mannequin equipped with "dummy head" microphones (a setup collectively called a "dummy head") to record the sound pressure from reproduced sound at the entrance of the ear under the recording environment and under the reproduced environment. These recordings are then compared and controlled in order to reproduce a realistic sound field.
The first step in this procedure is to use the dummy head to record the sound field to be reproduced. The dummy head is then installed in the sound-reproducing sound field and impulse responses, including head-related transfer function (HRTF) responses, are measured. The signal is then processed using a digital filter that eliminates crosstalk components in the sound-reproducing sound field. At this point, noise cancellation technology is used to process the sound reproduced by the speakers to match the recorded sound-pressure waveform at both ears of the listener. This allows a realistic reproduction of the sound field using two speakers rather than numerous speakers. Although reproduction systems using headphones are more common for stereophonic sound reproduction, it is difficult to localize the sound at a position away from the sound source and to reproduce low-frequency sounds. Moreover, the sound field being reproduced may vary with headphones depending on how the headphones are worn. At Nihon Onkyo Engineering, our sound-reproducing system uses speakers, allowing for superior playback compared with headphone-based playback systems for the reasons mentioned above.
Case study ― Designing and evaluating sound fields such as concert halls
In amusement facilities, realistic stereophonic sounds can have enormous effects on listeners. For the average stereophonic sound system, a variety of equipment such as speakers and amplifiers is required, making them expensive and costly. With the OSS, any sound field can be reproduced with high realism using a relatively small playback system with only two speakers.
Case study ― Three-dimensional acoustic effects at amusement facilities and event venues
In amusement facilities, realistic stereophonic sounds can have enormous effects on listeners. Common stereophonic sound systems include numerous speakers installed in a system that reproduces the intensity and time difference of sounds. However, these systems can be expensive and costly. In principle, the OSS is able to reproduce any sound field with high realism using only two speakers. This allows three-dimensional sound effects to be produced using a relatively small sound-reproduction system.
Case Study ― Evaluation of the in-vehicle sound field (noises, sound system)
Even at similar sound-pressure levels, sound evaluations will be different for each person depending on factors such as timbre. When it comes to evaluating sound in a passenger compartment, positive incorporation of specific sounds instead of simply silence as an added value to sound design makes it almost impossible to evaluate a sound space using simple acoustic indexes alone. In such situations, the basic and most effective evaluation is subjective evaluation. When performing evaluations using actual vehicles, problems such as driving situation reproducibility and time constraints exist. These problems can be resolved, however, by using the OSS to reproduce the in-vehicle sound field in the lab.
|Recording areas||Dummy head microphone sound source recording devices (digital audio tape, PC, etc.)|
|Sound reproduction areas||Convolution software amplifiers, speaker sound source reproducing devices (digital audio tape, PC, etc.)|
|Coefficient design areas||AEIRM impulse response measurement system filter coefficient design software|
|Common-use areas||Control PC high-performance audio interfaces|