Home Ministry Tech Leaders Sound System Upgrade: 4 Must-Know Concepts

Sound System Upgrade: 4 Must-Know Concepts

Early reflections actually contribute to speech intelligibility by increasing the total sound level while maintaining [the] coherence of consonant sounds. Early reflections also enhance musical clarity and allow members of ensembles to hear each other. Stage orchestra shells are basically made to create early reflections. Traditional church architecture often produces ample early reflections — usually mixed with mild reverberation — that encourage congregational singing.

Downsides – Again, no real downsides, unless the perceived boost in level from strong early reflections makes the overall sound too loud.

#3 – REVERBERATION

Definition – Reverberation is complex reflected sound energy that is perceived as separate from the direct sound. Reverberation “hangs in the air” after the direct sound stops. The nature of reverberation is defined by three characteristics:

Strength – How strong (loud) is the reverberant sound in comparison to the direct sound?

Decay – How long does it take for the reverberation to die away after the direct sound stops? This is usually given as a mid-band RT60, or the time it takes mid-band frequencies (those centered at 500 Hz and 1 kHz) to decay 60 dB from the initial level of direct sound. A very dead room, like a good movie theater, will be less than one second. A large cathedral can be 10 seconds or more, whereas a good symphony hall will be around two seconds.

Frequency balance – Depending on the size, architectural layout, and building materials, some frequencies in the reverberation envelope may be stronger than others. A persistence of low frequencies gives a “warmer” reverberation while higher frequencies will make the reverberation tail “brighter.”

Benefits – The right balance of reverberation can make a room “come alive,” for orchestral and choral music in particular. Reverberation contributes to a sense of depth and spaciousness, adding a dimensionality and enfoldment not realized with only direct sound and early reflections.

Downsides – Too much reverberation can be very damaging to speech intelligibility, as phase relationships crucial to recognition of consonant sounds become jumbled. Excessive reverberation also can be problematic with amplified music, with direct and reverberant sounds clashing with each other. Also, an imbalance in the reverberation envelope can make a room “boomy” (excessive low frequencies) or “edgy” (excessive high frequencies).

#4 – ECHOES

Definition – Echoes are discrete sound reflections that are perceived as separately identifiable sonic events. A slap echo is perceived as a single sound return, where flutter echoes are a rapid series of decaying echoes.

Benefits – Echoes can be great fun in a desert canyon but are universally problematic in church acoustics.

Downsides – Slap echoes can be generated in larger churches by a large flat or concave reflective surface at some distance from the stage. Sharp sounds, like a snare drum hit, will bounce back a discernible fraction of a second later and cause much consternation among the musicians.

Flutter echoes are caused by hard parallel surfaces, such as in a mirrored dance studio, and can be extremely annoying. Fortunately, flutter echoes are rarely generated in most church architecture, either traditional or contemporary.