Hisaharu Suzuki

Introduction of auditory filter into evaluation of characteristics of small enclosures

Physical measures, which are useful for evaluating small enclosures such as studios and car cabins, are examined. Especially, auditory filtering using Zwicker’s loudness model is introduced for calculating the measures. Most current measures used in evaluating the large sound field such as concert halls are based on measured or calculated impulse responses. Instead, the music signals of some genres are used in this study. Using the auditory model, the amount of information can be reduced, even when complicated signals are used as stimuli: the signals are convertible to information in 25‐bark bands. Correspondence of such physical quantities and subjective judgments are considered from the viewpoint of sound‐field similarity. Subjects are asked to judge the similarity of two successive sounds whose frequency characteristics are modified artificially using the equalizer. The analysis results obtained using the auditory filter were compared with the subjective evaluation. Results indicate that analysis using...

Selection of receiving positions suitable for evaluating acoustical parameters

Many physical parameters show characteristics of large sound fields such as concert halls. Some of them are adopted in the Annex of ISO 3382. That definition is clearly provided in ISO. However, practical measurement methods for them remain obscure. Our research is intended to examine an effective selection method of receiving positions based on the distribution of acoustical parameters in a real field. For that purpose, impulse responses are measured at more than 1400 seat positions to elucidate the distribution of acoustical parameters in an existing concert hall. The acoustical parameters, which are reverberation time, early decay time, clarity, and center time at each seat, are then calculated for 500‐Hz, 1‐kHz, and 2‐kHz octave bands. The distributions of reverberation time are quite even at all seats. However, the distributions of other parameters show symmetrical patterns at 500 Hz. At 1 and 2 kHz frequencies, the distributions show asymmetrical patterns in this hall. Based on the results obtained ...

Concept of active reverberation box

A quite small reverberation box with active controller system is proposed. If we try to measure the characteristics of acoustic materials, such as glass wool, in a small sized enclosure, there are few dominant modes which cause the condition that the incident wave to target material is biased toward the specific direction. As a result, the measured result shows the irregular distribution which depends on measuring point or evaluating method such as the reverberation time reading. The proposed system which utilized the active control enables us to create a plane wave with arbitrary direction in the enclosure. Therefore it has possibilities of solving the problems caused by insufficient incident condition. Also, in this study, the two evaluating strategies that the traditional reverberation time method and the steady state analysis method are concerned.