Acoustics is an extremely important factor in an ideal listening hall for orchestral music. And the desirable acoustic qualities of a listening hall can be credited to its overall architecture. Among the general characteristics that one should look for in an ideal listening hall include good sound projection even up to the back portion of the area; good articulation and clarity; good balance of both high and low frequencies; the absence of infuriating echoes; equal diffusion of sounds; and a feeling of ˇ°presence or ˇ°intimacy.
A good listening hall accomplishes efficacious sound projection up to the rear part of the hall so that distant listeners will be spared of extreme sound loss brought upon by the so-called inverse square law. It is the decrease of the sound pressure by 50% within a specific spherical wave front as distance is doubled. The projection is usually attained by having an extensive reverberation time.
Reverberation time is recognized as the period wherein the sound dies away as the sound source ends. However, this will have to rely on the sound's intensity. The most favorable reverberation time for an orchestral hall or any music room depends greatly on its expected purpose. Two seconds is the auspicious reverberation time for medium-sized hall that is intended for both music and speech uses. Meanwhile, a classroom should have a shorter reverberation time, while a recording studio must minimize its reverberation time for utmost recording clarity. Additionally, reverberation time is influenced by absorption coefficients of surfaces and also depends on the total volume of a particular music room. Longer reverberation time is not achievable in small rooms.
Furthermore, another significant aspect to note in an idyllic listening hall is a high and reflective ceiling to clearly reproduce the sound that reaches as far as the hindmost portion of the hall. As fullness
and richness of the hall reverberation is essential, such decreases the clearness of articulation. Thus, richness and fullness function against clarity. Equitable reverberation time should be thoroughly reached by a proper compromise of fullness versus clarity. Also, clarity may be fairly diminished by unwelcome echoes. At certain locations within the hall, clarity of sounds can be reduced by any factors that block any part of the sound; hence, amplifies a fraction of the reverberant sound that reaches the listener.
Achieving the apt balance between low and high sound frequencies particularly at the end of the hall is normally a matter of enhancing the bass. Once the listening hall has shorter reverberation time and comes to terms with the inverse square law, most likely, bass loss problem will be encountered. Most halls partially overcome bass loss problem by having reverberation time for lower frequencies that is longer than high frequencies.
To continue, sound is undeniably more pleasant to hear if evenly dispersed, which means, no significant ˇ°live or ˇ°dead spots in the hall, and no high-flying echoes. Even dispersion is typically achieved by evading huge flat areas and focusing surfaces that reflect the sound unto the listing area. Other times, it is even deem desirable to put on few anti-focusing surfaces.
Besides the primary features of an ideal listening hall for orchestral music, there are still some nuances that cause listeners to want some other listening halls over others. Such desire is the need for certain preferences such as ˇ°musical presence, ˇ°intimacy, or the listeners' desire to feel that they are so much part of the whole performance, not secluded from it. And the basic factor that is more related with such preference is the period between the initial reflected sound and the direct sound that reaches the listeners. As quantitative studies put it, the primary reflected sound must arrive within 30 msec from the direct sound. A 50 msec lag time or more already draws out negative reactions from the listeners.
