Friday, February 29, 2008

Of Music and Sound Levels: Hurting Each Other

All of us know that very loud sounds can damage our ears but what if it is required in a particular piece of music, is this the end of artistic integrity?

By: Vanessa Uy

For over a year now, my audio and music buddies have been actively speaking out about the role of loudness / decibels i.e. sound pressure levels in maintaining the artistic integrity of a piece of music. When it comes to loudness levels, the genre of music that usually gets the flack is the modern 20th Century variety like Rock & Roll, Disco and especially my favorite Heavy Metal Music. But the controversy surrounding the issue seems to be born out of ignorance. Almost nobody raises an issue or blame my other favorite form of music, namely Symphonic Classical / Romantic Music. A live Symphony playing a particularly loud piece can easily drown out the racket produced by an M-16 assault rifle fired in full automatic mode 30 feet away from you. And my current audio system can play that loud cleanly, the only sign I know that I’m playing to loud is when my ears ring afterwards. A really great sound system is really dangerous because you won’t know it’s hurting you ears but the damage produced like tinnitus is cumulative. But before going any deeper, let me try to dispel some myths surrounding loudness before our politicians legislate laws that violate the laws of physics.

Sound pressure levels – the one that travels in air since “almost all” live musical performances are performed on dry land – is measured in decibels. Decibels are determined on a base 10 logarithmic scale. So a sound wave that measures 10dB SPL (decibels sound pressure level) has ten times the acoustic (sound) energy than a sound wave measuring just 1dB SPL. 20 dB SPL has 100 times more energy than 1dB SPL and 30dB SPL has 1000 times more acoustic energy and so on progressing logarithmically. And since our ears perceive sound levels logarithmically we hear sound differently from artificial conveyances like microphones. Imagine two sound sources, a sound wave has to be ten decibels louder than another in order for us to perceive it to be twice as loud. So, what does the measured sound pressure levels of the sound that we hear in everyday (to me) life? An ordinary conversation 3 meters in front of us measures 60 to 70 dB SPL. A Symphony Orchestra in the loudest musical passages (especially pieces by Richard Wagner and Gustav Mahler) can generate 120 dB SPL as does a Heavy Metal concert held in a typical stadium. And that’s only a couple of decibels shy than a military fighter jet taking off with afterburners fully aflame. A typical assault rifle that uses 7.62mm NATO round generates about 130 dB SPL or a bit louder (measured using Radio Shack’s “relatively inexpensive” but sufficiently accurate 33-2050 Sound Level Meter) when fired in full automatic mode inside a tiled bathroom. 20th Century era artillery pieces, like howitzers usually approach or go over 140 dB SPL and generating sounds louder than this can become impractical because we are now reaching the “linearity limit” i.e. the acoustic power input = acoustic power output of air. That’s why military / naval SONARs that can get as loud as 230 dB SPL is never tested on dry land (in air) since their sound waveform can get distorted not to mention the racket it can create.

On the more tranquil side of the scale, 40 dB SPL is the loudness level of the softest note used in a musical score “technically” referred to as “pianissimo”. 30 dB SPL is the sound level found in a residential neighborhood at 2 in the morning when there is no electricity. 20 dB SPL is the level of ambient noise in a typical multi million dollar recording studio that’s acoustically treated properly (Don’t you just hate those people who claim that their sub-prime mortgaged “el-cheapo” houses are this –20 dB SPL - quiet?). Zero / 0 dB SPL can only be achieved inside an anechoic chamber commonly referred to as “the dead room” like the one found in Bell Laboratories. Anechoic chambers / dead rooms are pretty eerie places because if the person inside talking to you is not in the line of sight to your ears you can never hear them, even if they are only a few feet away from you.

There was a news story aired on DW-TV’s People and Politics last February 12, 2008 about the expanded plan to amend current laws concerning noise abatement in the workplace. The most “ridiculous” place targeted by the planned noise abatement in the workplace law were Germany’s world class Symphony Orchestras. It was shown on that piece that even a flute generates over 100 dB SPL within 30 centimeters (1 foot) from the instruments “bell”. Tinnitus could ruin a professional musician’s career. Currently legislated worldwide laws regarding occupational safety in the workplace requires anyone exposed to sound levels over 85 dB SPL over an eight hour period be required to wear ear plugs / ear muffs. To me, this law is extremely ludicrous because the first hand experience of my friends who worked in the music business since 1989 had never come across ear - plugs / ear protectors that are tonally transparent. Ear - plugs just spoils our enjoyment of the musical instruments proper timbre. Ear - plugs are nothing like the volume controls of our audio playback systems. I’ve tested one that’s designed back in 1992 exclusively for jazz musicians (still sold at the exorbitant sum of US$200 after all these years) and was touted to be acoustically transparent. The sound levels going to my ears did become softer but also extremely dull, all of the high frequency sounds went on hiatus. Though not as dull as the ones used for gun practice that’s commonly sold for only half a dollar per pair.

So what does this all mean? First of all, lawmakers everywhere should familiarize themselves with the laws of physics because we cannot easily repeal those as easily as legislated / man-made laws. Just imagine if we could amend the law of gravity, commercial aviation could become very cheap and non-polluting, space tourism would become available to anyone. If we could just repeal the laws governing sound of acoustics, the world would be a happier more aesthetically pleasing. But we can’t, we can only work in harmony with the physical laws that govern sound and acoustics. The sooner our policymakers realize it, the sooner sensible laws governing the auditory health / occupational health and safety of our professional musicians can be legislated. Just remember that tinnitus is still incurable, so Rock On responsibly.