Unplugged Sound
What? How Loud?
Anton Niedersteiner - Acoustic Sound Reinforcement & Audio Engineering
At an outdoor jazz event I glanced at the meters to get a rough idea of the power drain on the amps. I was surprised to see them peaking in the middle of the green. The board was 100' from the stage. The mix was comfortably loud, all instruments well balanced and every detail was evident. I asked my assistant to guess what the SPL was. He replied, "Oh, about 100 to 105dB". I bring out my meter and measure 86dBA.
In his book "Sound for the Theatre", Graham Walne writes about a similar experience. He was consulted on a replacement system for a large venue. The owner wanted 120dB based on the old system but was persuaded to accept 108dB on the merits of improved clarity. This client actually runs the new system at 80dB.
Throughout modern history, music, instruments and groups, and performing spaces have evolved with continuos improvements and refinements. The only constants being the physics of acoustics and our hearing abilities. The latter being the final evaluator and judge of the listening experience. Consider chamber music for instance. The way the music is written, the instruments it is played on and the venue in which it is played are all inter-related, each complementing the others. If the same music is played on the same instruments in a large venue (such as a school gymnasium) it would lose it's intimacy, warmth and charm. The experience would be lost. One could make improvements by rearranging the music, adding more instruments and altering the acoustics. With enough refinement you would end up with symphony music, played by a symphony orchestra in a symphony hall. It would again be a pleasant experience, all be it different. The constant factor throughout this process has been our hearing. Everything is relative to that.
Although loudness is subjective, enough tests, measurements and evaluation have been conducted to provide a fairly accurate understanding of how most people interpret loudness or volume. The Fletcher/Munson work is the most quoted and generally undisputed. Sound pressure levels (SPL) of 60 to 80dBA are considered loud, 80 to 100dBA are very loud, 100 to 120dBA deafening. (Subjective terms supplied by M. David Egan, Architectural Acoustics.) Not surprisingly, maximum levels of acoustically generated music fall within the first two categories, nearby thunder being in the last. The advent of electronic amplification systems has propelled music into the deafening and even painful categories. This has now become an issue.
One side of the issue is our concept of pleasure. Many people find extremely loud music to be pleasing. The adrenalin rush initiated by the high SPL heightens the excitement of the music itself. Powerful bass rhythms are literally felt in the body. Sharp piercing melody lines cut deep into the soul. We are blanketed in a wash of energy. These are new experiences in the history of music. Experiences brought about by new music styles, new music instruments, and new higher SPL capabilities, together forming the experience.
The other side of the issue is safety. Prolonged exposure to high sound pressure levels causes hearing damage. Governments have in place legislation limiting workplace noise levels and exposure times. Often musical events far exceed these limits. (Hmmm... it seems more thought should be given here.)
Summarizing these three points quickly focuses the issue: 1, High SPL is dangerous. 2, Only certain music is suited to being played so loudly. 3, If the system is clean, it will seem louder than it actually is.
I set my limit at 100dBA and as evidenced in the example above, I often don't need to be anywhere near that.
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