水平面内における方向定位 (<特集>聴覚)
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概要
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This paper describes the sound localization on the horizontal plane. Fig. 1 shows the Loudspeaker arrangement for the experiments of directional hearing made. An observer sits on a chair with a headrest as shown in Fig. 2. The observer's head is slightly supported by the headrest. The observer gives the perceived direction of sound source presented. The results of the experiments of the directional hearing for these one-octave band noises can be divided into two groups (Fig. 3, 61%, and Fig. 4, 35%). The perceived direction of the observers of Fig. 3 is influenced by the signal frequency and the sound pressure level but that observers of Fig. 4 is not influenced by these factors. Table 1 shows the percentage of observers for each signal frequency and each judgement type. It is noteworthy that only the 8k - 16kHz one-octave band noise gives the correct judgement (74%). As for other four signals, the misjudgements are influenced by the signal frequency and the sound pressure level. As for the phantom sound source (see Fig. 7), the directional hearing for the one-octave band noise is shown in Fig. 8 and there occur many misjudgements. It is also noteworthy that the phantom sound source in the direction of 45゜ - 135゜ are not perceived in the direction of 45゜ - 135゜ but in the direction of 45゜ or 135゜ and that this phenomenon still occurs even if the band width of the signal becomes two octaves (Fig. 9). In order to find the factor which is effective for the correct judgement, three additional experiments are tried, the directional hearing of the real sound source, of two-octave band noise (Fig. 5), and of one-octave band noise with a certain amount of 8k - 16kHz one-octave band noise (Fig. 10), and the male voice cut off by a Low-Pass-Filter (Fig. 6). By these experiments, it may be said that the sufficient amount of the component of 8k - 16kHz, and widening of signal band are effective for the correct judgement and that the former is far more effective for the correct judgement and that the former is far more effective than the latter. Table 2 shows the percentage of observers of each one-octave band noise whose perceived direction is influenced by the sound pressure level. The ratio of observers whose perceived direction is influenced at least by two kinds of one-octave band noise is 53%. The relationship between the perceived direction and the sound pressure level is shown in Fig. 11 as a typical example. The perceived direction is determined independently of the loudspeaker direction. The last problem is the perceived direction of phantom sound source in the direction 45゜ - 135゜. This phenomenon can be explained by the calculation of ？P and ？ψ, where？P is the difference of the sound pressure level and ？ψ is the difference of the phase at the entrance of two external auditory canals (See Fig. 12 and Eq. 1 - Eq. 8). The results mentioned above are under the condition that the observers heard the signals in an echoless chamber with their head supported. Fig. 13 shows the relative frequencies of the directional hearing of 1/3-octave bands noise under the ordinary condition, without a headrest and in a laboratory room There still occur many misjudgements. These results and discussions can be applied to the recording technique of the 4-channel stereo.
- 社団法人日本音響学会の論文
- 1974-03-01