Gilbert A. Soulodre

The influence of late arriving energy on spatial impression

New subjective experiments using sound fields simulated in an anechoic room confirm that spatial impression in concert halls is composed of at least two distinct aspects: apparent source width and listener envelopment. Previously published research has shown that apparent source width is related to the relative level of early lateral reflections. This new work demonstrates that listener envelopment is related to the level, direction of arrival, and temporal distribution of late arriving reflections. It is further shown that increased amounts of listener envelopment decrease the subject’s sensitivity to changes in the apparent source width of the sound field. Listener envelopment is related to objective acoustical measures, and the implications for concert hall design are discussed.

Subjective evaluation of new room acoustic measures

A series of experiments were conducted to evaluate several acoustical measures as predictors of subjective judgments. Subjects were asked to rank binaurally reproduced sound fields in terms of loudness, clarity, reverberance, bass, treble, envelopment, apparent source width, and overall preference. The binaural impulse responses were measured in several North American concert halls and were chosen so as to cover as broad a range as possible of RT, EDT, C80, G, IACC, and LF values. The results of these tests were then correlated with the various octave‐band objective measures to find the best predictor of each subjective parameter. New objective quantities were found that are correlated with loudness, clarity, bass, and treble judgments. The relative importance of the various subjective parameters to the overall preference of these sound fields was also examined.

Modeling of the seat dip effect using the finite‐difference time‐domain method

In this paper the use of the finite‐difference time‐domain technique for the modeling of the seat dip effect in concert halls is demonstrated. The linear time‐domain acoustic partial differential equations are discretized using a finite‐difference technique. The second‐order accurate differencing scheme is time–space centered, and the velocity and pressure are solved on an interlaced mesh. First‐ and second‐order Mur absorbing boundary conditions, originally formulated for electromagnetic problems, are adapted to the acoustics case and used to truncate the numerical grid. The technique is first verified by comparing the numerical results to the analytic solution of a simple point source. Results from computer simulations of the seat dip phenomena are compared with the findings of previous studies where measurements had been made on scale models and in real concert halls. The computer model successfully predicts the effects associated with the source–receiver distance, the height of the receiver, and the h...

Factors influencing the perception of bass

It is commonly assumed that low‐frequency reverberation time determines the perception of bass in concert halls. Laboratory experiments were conducted to evaluate whether this and other factors influence subjects’ perceptions of the strength of bass sounds in simulated sound fields. The levels of the early and late arriving low‐frequency sounds as well as low‐frequency reverberation times were systematically varied. Ten subjects rated the strength of the bass content of the music for each sound field on a five point scale relative to a reference sound field. Both the levels of the early and late arriving low‐frequency sound had significant effects on the judgments of the bass content. Low‐frequency reverberation time was not significantly related to subjective ratings of bass. The direction of arrival of low‐frequency sound had smaller effects on the assessments of the bass content in the sounds. The results suggest that increased low‐frequency reverberation time is not important for increasing the sense ...

The acoustics of concert halls

The most important characteristic of any concert hall must be the sound that it delivers to the listener. While the acoustics of a hall are unlikely to make a good orchestra sound bad, a well designed auditorium can provide a truly memorable experience. Yet the Boston Symphony Hall, which opened in 1900, was the first to be designed with the science of acoustics in mind.

The influence of low frequency energy on listener envelopment

The importance of low frequencies to the perception of spatial impression in concert halls and multi‐channel surround systems is well established. The present paper reports the results of a series of subjective tests that demonstrate the influence of low frequency lateral energy on the perception of listener envelopment. The results show that the laterally‐arriving low frequency energy contributes significantly to listener envelopment, and new objective measures of listener envelopment are derived that account for this effect. The effect of the spatial distribution of low frequency energy on the perception of Bass is also discussed.

Acoustical renovation of The Opheum Theatre, Vancouver Canada

The Orpheum Theatre is a 2800 seat vaudeville house that was renovated for the Vancouver Symphony in the 1970s. Funds ran out prior to completion and some problematic conditions remained for the following fifteen years. Perhaps the most significant was an image shift heard on the balcony. Two focused reflections arriving at approximately 50 ms made some source locations on the stage appear to be perched in the ceiling. The efficacy of the plastic reflectors above the stage was also questioned. These and other issues were addressed with a complete set of stage and audience measurements in the full‐scale room, experiments with a 1:48 small scale model, and listening tests using anechoic music convolved with the full‐scale binaural impulse responses. The latter was particularly important because it allowed for reliable quantification of image shift thresholds that were unique to this room. Small scale modeling proved useful in matching the new convex reflectors’ radii of curvature to the image shift threshol...

A preliminary analysis of image shifting in concert halls

Under typical conditions, the early reflections in a concert hall are attenuated relative to the direct sound and are thus integrated with the direct sound. However, there are instances where, due to focusing effects, the level of a reflection can be greater than or equal to the level of the direct sound. This can result in an apparent shifting of the image away from the true source and toward the source of the reflection. This paper reports on a series of subjective tests designed to provide an initial look at the parameters of the reflected sound which influence image shifting. Tests were conducted using two methods: binaural simulation and multiple loudspeakers in an anechoic chamber. Image shifting was examined as a function of the level, delay, angle of arrival, and spectral content of the reflected sound relative to the direct sound. The results were examined in the context of the Orpheum Theatre in Vancouver where pronounced image shifting occurs at certain locations in the hall due to several larg...