The spatial information contained in measured room impulse responses can be used to explain some of the acoustical properties of performance spaces. This paper presents a spatial encoding method, which can extract accurate spatial information from impulse responses that are measured with at least four microphones in an open 3-D array. The method is based on decomposing a spatial room impulse response into a set of image-sources, i.e., every single sample in the impulse response is considered as an image source. Each of the image-sources is localized with an acoustic source localization method, which depends on the applied microphone array and the acoustic conditions. Due to the image-source presentation, the presented method can be applied to any compact array and used in conjunction with variety of current spatial loudspeaker reproduction systems to create convolution reverb-type spatial sound reproduction. The method allows static and interactive binaural reproduction via virtual loudspeaker arrays. The presentation includes demonstrations with a binaural reproduction system.

Subjective evaluation of acoustics was studied by recording nine concert halls with a simulated symphony orchestra on a seat 12 m from the orchestra. The recorded music was spatially reproduced for subjective listening tests and individual vocabulary profiling. In addition, the preferences of the assessors and objective parameters were gathered. The results show that concert halls were discriminated using perceptual characteristics, such as Envelopment/Loudness, Reverberance, Bassiness, Proximity, Definition, and Clarity. With these perceptual dimensions the preference ratings can be explained. Seventeen assessors were divided into two groups based on their preferences. The first group preferred concert halls with relatively intimate sound, in which it is quite easy to hear individual instruments and melody lines. In contrast, the second group preferred a louder and more reverberant sound with good envelopment and strong bass. Even though all halls were recorded exactly at the same distance, the preference is best explained with subjective Proximity and with Bassiness, Envelopment, and Loudness to some extent. Neither the preferences nor the subjective ratings could be fully explained by objective parameters (ISO3382-1:2009), although some correlations were found.

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Concert hall acoustics was evaluated with a descriptive sensory analysis method by employing an individual vocabulary development technique. The goal was to obtain sensory profiles of three concert halls by eliciting perceptual attributes for evaluation and comparison of the halls. The stimuli were gathered by playing back anechoic symphony music from 34 loudspeakers on stage in each concert hall and recording the sound field with a microphone array. Four musical programs were processed for multichannel 3D sound reproduction in the actual listening test. Twenty screened assessors developed their individual set of attributes and performed a comparative evaluation of nine seats, three in each hall. The results contain the distinctive groups of elicited attributes and show good agreement within assessors, even though they applied individual attributes when rating the samples. It was also found that loudness and distance gave the strongest perceptual direction to the principal component basis. In addition, the study revealed that the perception of reverberance is related to the size of the space or to the enveloping reverberance, depending on the assessor.

Acousticians and other practitioners alike often describe acoustic conditions in performance spaces with standard objective parameters. Apart from a few exceptions, the parameters are calculated by integrating the sound energy of the impulse responses over time; this makes them inadequate for researching the acoustics in detail, especially in the early part of the room impulse response. This paper proposes a method based on time-frequency and spatiotemporal presentations to overcome the lack of detail in the standard analysis. In brief, the proposed methods visualize the cumulative development of the sound field as a function of frequency or direction by forward-integrating the energy in the impulse response in short time frames. Analysis on the measurements from six concert halls concentrates particularly on interpreting the results in light of the seat dip effect. Earlier research has concluded that the seat dip effect is reduced by reflection from low overhead surfaces. In contrast, the current results indicate that the seat dip attenuation in the frequency response is corrected the best when the hall provides most lateral reflections. These findings suggest that the proposed analysis is suitable for explaining concert hall acoustics in detail.