Toshiki Hanyu

A new objective measure for evaluation of listener envelopment focusing on the spatial balance of reflections

Abstract We conducted seven subjective experiments in order to clarify the effects of the arrival direction and spatial distribution of reflections on listener envelopment (LEV). As a result, it became clear that the contribution of a reflection to LEV depends on the arrival direction of other reflections, and that making independent evaluation is not entirely a possibility. For our sound fields, LEV cannot be optimally evaluated with objective measures that weight and integrate individual reflections by the arrival direction like that of lateral energy ratios. It is necessary to consider the mutual effects of these reflections by some means and to quantify their spatial distribution of reflections. Accordingly, we have proposed a spatially balanced center time ( SBT s ) for quantifying the spatial distribution of reflections using center time T S for each direction, and have demonstrated that it is possible to obtain adequate correlations with the psychological scores of LEV.

Analysis Method for Estimating Diffuseness of Sound Fields by Using Decay-Cancelled Impulse Response

An analysis method for estimating diffuseness of sound fields by measuring the time variation in reflected sound energy of impulse responses is proposed. In this method, first a decay-cancelled impulse response is obtained by removing the reverberation decay from the impulse response using a Schroeder decay curve. The degree of diffusion of the sound field is determined by evaluating the time variation in the reflected sound energy of the decay-cancelled impulse response. By using this method, the frequency characteristics of diffuseness in sound fields can be analysed from the impulse response measured at a single point. The average degree of diffusion in a room can also be evaluated by averaging the analysis results at several points in the room, similar to the analysis of reverberation time. In order to verify the proposed method, the impulse responses in rooms having different types of diffusers were calculated by the wave acoustics computer simulation. The frequency characteristics of diffuseness were analysed from the calculated impulse responses, by using the proposed method. The results showed that the frequency characteristics of diffuseness change depending on the size of the diffusers. Thus, the proposed method can be used for evaluating the effect of diffusers on the degree of diffusion in a sound field.

Speech privacy at community pharmacies

To identify practical ways to assess privacy protection at counseling area in community pharmacies, we conducted site-visit investigations at 84 community pharmacies including on 10 telephone interviews, and internet questionnaire survey on 160 patients. In the typical Japanese community pharmacies, space is small, the counseling area is open, and there are many patients who are waiting until their name is called. In that situation, busy and noisy and loose concentration, patients must try to accurately grasp medical information, and pharmacist are also working in the same situation. At the site-visits, we asked about aural or visual privacy issues and performed a psychological experiment to determine whether the patient-pharmacist conversation could be heard from the waiting seats for patients. At the internet questionnaire, we asked about counseling environment at community pharmacies. Responses to the site-visit investigation and internet questionnaire survey revealed that privacy-related problems were...

Influence of acoustic envelopment on spatial impression

The spatial information of a sound field in various kinds of halls has been measured and studied. Through these measurements, it is clear that not only early lateral reflections (which relate strongly to spatial impression [M. Barron, J. Sound Vib. 15(4), 475–494 (1971)] but also acoustic envelopment were some of the characteristics of the spatial information. Therefore, quantifying acoustic envelopment, and examining the influence of acoustic envelopment on spatial impression by performing experiments has been tried. The results are as follows: (1) Acoustic envelopment influences spatial impression, especially in regards to subjective envelopment; and (2) there is a possibility that subjective envelopment can be explained by the values (e, b, A.E.) that have been introduced in order to quantify acoustic envelopment.

Theoretical model of reverberation decay in a rectangular room—Potential for predicting flutter echo

Reverberation is the most important factor governing the acoustic design of a room. It is known that non-exponential reverberation decay may occur in a room with unevenly distributed sound absorption, namely, with non-diffuse sound field. We propose the theoretical model of reverberation decay in non-diffuse sound fields. The reverberation decay is characterized by absorption and scattering properties of the surfaces of a room. As a first step for developing reverberation theory of non-diffuse sound field, the proposed model deals with rectangular rooms, because rectangular rooms are very common in any kind of buildings and architecture. Spatial absorption coefficients for three orthogonal directions are defined as the parameters which characterize the energy decay curve in the rectangular room. Within this model, the reverberation in such rectangular room becomes a combination of exponential and power law decay. The power law dependence as a function of time has a singularity. This issue is resolved with...

Evaluation of spatial impression of sound field in a concert hall based on the sound intensity using musical sounds

Spatial impression is one of the most important factor for evaluating sound fields in concert halls. Objective indices, such as the lateral energy measures, for evaluating the spatial impression are standardized in the ISO-3382. These indices can be measured by using a figure-of-eight pattern microphone. On the other hand, details of spatial information of sound field can be depicted by measuring instantaneous sound intensity in the sound field. However, thus far, there is no index using the sound intensity. In this study, first the relationship between the existing objective indices and the sound intensity is examined. In particular, the existing objective indices are redefined based on the sound intensity. Secondarily, some objective indices are newly defined by using the sound intensity. These intensity-based indices can basically be calculated by using the sound intensity of impulse responses in a room. Third, potential of measuring the intensity-based indices by using musical sounds is examined. We i...

A fundamental study of evaluating sound fields in performance spaces based on equal tempered scale

Generally, the reverberation times, energy decay curves, directional characteristics, and so on are analyzed in 1 octave bands or 1/3 octave bands for evaluating acoustic conditions in performance spaces. The center frequencies such as 1000 Hz are defined by engineering implication. However, these center frequencies are not always adequate for evaluating performance spaces because music is basically composed of musical scale like the equal tempered scale. Therefore, it is thought that it is reasonable to use center frequencies based on the equal tempered scale in order to evaluate performance spaces. Based on this idea, we calculated reverberation times and energy decay curves for 1/12 octave bands at which center frequencies are set by using the equal tempered scale. Directional characteristic of reflected sounds is an important factor for evaluating spatial impressions in performance spaces. Therefore, we measured the directional characteristics based on sound intensity in the 1/12 octave bands. Moreove...

Theoretical Modeling of Room Shape for Ray Tracing Simulation

With the recent developments in computer-aided design (CAD) technology, the detailed modeling of shapes has become routine. However, it is well known that low-frequency sounds do not propagate in detail-oriented models of rooms in the way that is predicted by geometrical acoustic simulations. Therefore, rough models of room shapes are commonly used and scattering coefficients are set for each material in this kind of simulation. However, scattering coefficients are difficult to use for creative room shape design, because scattering coefficients need to be measured in advance. Thus, we propose a new method for ray tracing simulations that can be used in place of the scattering coefficient method. This paper presents a discussion of methods for constructing the appropriate room shape for the analyzed frequency from a detail-oriented model of a room.

Spatial impressions from late overhead reflections in concert halls

It is known that not only late lateral reflections but also late overhead reflections contribute to listener envelopment (LEV) which is one of the perceptive factors in the spatial impression of sounds in a concert hall. This paper describes results of psychological experiments which are intended to clarify differences between spatial impressions of the late overhead reflections and that of the late lateral reflections. The results are the following: (1) Late overhead reflections have a different acoustic effect from late lateral reflections. (2) Late overhead reflections increase not only LEV but also overhead sound image (OSI). (3) Late lateral reflections contribute mainly to horizontal listener envelopment (HLEV). (4) If OSI is increased in addition to HLEV, a listener feels vertical listener envelopment (VLEV).

A theoretical framework for quantitatively characterizing sound field diffusion and sound energy decay curves based on the scattering coefficients and absorption coefficients of walls.

A theoretical framework for characterizing sound field diffusion based on the scattering coefficients and absorption coefficients of walls was developed. The concepts of the equivalent scattering area, equivalent scatter reflection area, average scattering coefficient, and average scatter reflection coefficient are introduced in order to express each room’s capability of scattering. Using these concepts and the mean free path, the scatter‐to‐absorption ratio, mean scatter time, and the diffusion time are defined in order to evaluate the degree of diffusion of a space. Furthermore a theoretical model for characterizing sound energy decay curves in a non‐diffused sound field based on the above mentioned concepts was also developed. First a reverberation model for a room which consists of perfect specular reflective walls was examined. Second the scattering coefficient was introduced to the above reverberation model in order to consider the effects of the sound scattering from the walls on the energy decay c...