This post discusses sound levels (loudness) in public places and on the radio. It is partly a rant based on what I take to be carelessness in setting or maintaining levels, but is also a discussion about aspects of sound levels that I think are important for anyone working in sound to know, including how loud sound can damage one’s hearing.
SOME BASIC TERMS
Sound consists of vibrations of molecules in the air. Sound can travel through hard surfaces as well, but the everyday sounds we use are carried in the air. They are a series of compressions and rarefactions (the opposite of compression) of the air molecules. Without a medium there can be no sound, as in outer space. Light consists of quantum particles and can travel through space, but sound cannot. That is why we can see the explosion of a star but never hear it.
When we talk about sound we often talk about the frequency (pitch) of a sound, it overtone structure (usually called timbre) and its amplitude (usually called level or loudness).
In this post I only want to talk about the levels (amplitudes) of sound.
The acoustics of public spaces can very widely, especially in restaurants, bars, and similar recreational spaces not designed specifically for performance. A church, theatre, or concert hall will usually be designed for listening quietly at least from time to time. But a restaurant can be extremely noisy. Some of this is based on the number of people, the design of the space, and the use, or lack of use, of sound deadening materials. Hard surfaces reflect sound easily, with little absorption, yet many restaurants and bars think certain hard surfaces look cool. Also, some seem to think that lots of noise in a place translates into lots of fun, so they don’t care about the noise generated by patrons.
But in this post I want to talk about noise generated artificially, most specifically music played in restaurants and bars. OSHA, The Occupational Safety and Health Administration, is an arm of the United States Department of Labor and sets many safety standards for workplaces.
A more detailed discussion of sound levels for the workplace can be found on the following website on a post called “How Loud is Too Loud.” (https://www.osha.gov/SLTC/noisehearingconservation/loud.html)
I will quote a key passage from it:
“OSHA sets legal limits on noise exposure in the workplace. These limits are based on a worker’s time weighted average over an 8 hour day. With noise, OSHA’s permissible exposure limit (PEL) is 90 dBA for all workers for an 8 hour day. The OSHA standard uses a 5 dBA exchange rate. This means that when the noise level is increased by 5 dBA, the amount of time a person can be exposed to a certain noise level to receive the same dose is cut in half.
The National Institute for Occupational Safety and Health (NIOSH) has recommended that all worker exposures to noise should be controlled below a level equivalent to 85 dBA for eight hours to minimize occupational noise induced hearing loss. NIOSH has found that significant noise-induced hearing loss occurs at the exposure levels equivalent to the OSHA PEL based on updated information obtained from literature reviews. NIOSH also recommends a 3 dBA exchange rate so that every increase by 3 dBA doubles the amount of the noise and halves the recommended amount of exposure time.
Here’s an example: OSHA allows 8 hours of exposure to 90 dBA but only 2 hours of exposure to 100 dBA sound levels. NIOSH would recommend limiting the 8 hour exposure to less than 85 dBA. At 100 dBA, NIOSH recommends less than 15 minutes of exposure per day. ” From: https://www.osha.gov/SLTC/noisehearingconservation/loud.html
I bring up these levels because many people, in headsets or over speakers in bars and clubs, listen to a much higher level than OSHA recommendations and often for long periods of time. Many people would be surprised that these upper limits are not as loud as some suppose. If you want to check a level it is easy to buy a sound pressure level meter. Even Radio Shack has been known, at least in the past, to produce an inexpensive one. Many are available on Amazon.
What especially bothers me is that even schools and organizations whose intent is to protect people often seem not to worry about sound levels at social events. When I was an academic department head at a college the faculty were called into a meeting about behaviors to protect students. I was in my 50s at the time but we were all assured that our 18-20 year old female students would be damaged if we, as middle aged professors, happened to refer to them as “girls” rather than as “women.” I am not a psychologist so I don’t know whether this causes damage to a young woman or not, but I am always happy to call people by the words they prefer. No problem there, though since I often hear women of all ages referred to as “girls” on British radio, I am not sure if the Brits just don’t worry about psychological damage, or if they don’t really believe there is medical evidence.
A couple of hours after that meeting at the college the same school held a social event where an extremely loud rock band was playing. It was so loud I, myself, could not stand to be in the room. I brought out my trusty sound pressure meter and indeed the level was way beyond what OSHA says is safe even for 15 minutes. The studies of sound pressure to hearing damage is hard, very provable, science. If you go to a loud club and when you walk out you have the sensation that your ears feel a little numb, than hearing damage has started. Do that regularly and the hearing loss will become permanent. Early rock band players who stood for hours in from of high pressure Marshall stacks, or the equivalent, found out in middle age that they had substantial hearing loss. Now many wiser young band members who play in very high volume bands wear hearing protection.
If you must be in loud environments, either for work or entertainment, there are measures you can take to help protect your ears.
Earplugs: These can be very inexpensive foam plugs that are far better than nothing. They are so inexpensive that nobody can reasonably say they cannot afford them. Many drugstores carry them. There are companies that make higher end plugs that are more comfortable, less obvious, more effective and are sometimes designed so that conversations can be more easily heard in a noisy environment. Some are even custom fitted to one’s own ears, but those can be very expensive.
Isolation headsets: People who work around jet engines (which are extremely loud) need headsets which simply block out a significant amount of noise. I have seen this kind of hearing protection also worn by road crews near jackhammers and even some lawn care workers with very noisy riding mowers. I have also seen these wisely used in indoor shooting ranges.
But what if someone wants to listen to music or podcasts in a noisy environment but want to protect their ears? There are two solutions here also:
Isolation headphones: These are audio headphones built into the same kind of hearing protection that jet engine workers use. I don’t shoot guns or work on jet engines, but when I record a live classical concert and need to sit, with my gear, very near the front of the hall, I need to monitor the feed from my recorder without too much mixing with the direct stage-to-ear music. For that I wear isolation headphones. My current personal preference is the TELEFUNKEN Elektroakustik THP-29 Isolation Headphones which cost about $135 on Amazon. Other brands are available on Amazon from slightly over $50 to nearly $200.
Noise cancelling headphones or earbuds: These are less for hearing protection from extremely high noise levels, than to make listening to music or podcasts more comfortable in an environment with some continuous noise, such as on a plane or train. I always take a pair on an overseas flight. They allow for music listening but greatly lesson the drone of the jet engines. Because of how they lessen continuous noise (by cancelling the noise with itself out of phase) they are better for continuous drone-type sounds than for conversations. But that is good. One can still hear the announcements made by the flight crew even while listening to one’s phone or music player.
Models that are very popular with travelers include those made by Bose, who tend to advertise in flight magazines. They are very good but other brands work also. My own pair is made by Sennheiser which I like because they are a bit smaller than the Bose phones though I think the model I own is no longer in production. There are even noise cancelling earbuds, but I have never tried them. Some are “active” and work like the noise cancelling headphones I have just described, but some just reduce noise by blocking sound entrance to the eardrums, more like isolation phones, but I am not personally fond of having things put that far into my ear.
OTHER LEVEL ISSUES
I am a big fan of radio. I own four wifi radios which let me listen to stations all over the world via my home wifi including the several radio services of the British Broadcasting Company (BBC) and even small public radio stations in the US that do interesting local programs, but are outside the range of over-the-air tuning for me. Almost all U.S. radio stations transmit an internet sound stream as well to their regular AM or FM transmissions.
There can be a problem with variation of levels within a program or between programs. If a station is a local all-talk or all rock-music station they usually broadcast at a uniformly high volume. They even use devices often called “companders” to make softer parts loud and to keep loud parts below the maximum legal transmitter modulation level. This keeps them loud on the dial so someone tuning stations notices when they pass it while searching. This works for music intended to be consistently loud or for talk at the same level — simply broadcast it as loud as legal.
The problems come with music intended to be heard with both loud and soft passages – classical especially but also some jazz and folk. Classical stations can be hard to find when one is tuning up the dial in an unfamiliar area. If a classical station happens to be broadcasting a very soft musical passage, someone might tune past the station without realizing there is a signal. (This is not a problem with internet streams as those are tuned by internet addresses, not by listening for sound while changing the tuning.)
But a problem can result when trying to balance the studio announcer against the music. Obviously one does not want the talking to be as loud as a loud orchestra swell, but what makes a good balance? Often on a Sunday night I listen to a mid-west (US) public station that runs a kind of minimalist music that borders almost on “new age” that is good to hear softly while relaxing in bed before sleeping. But the presenter who identifies the artists talks and sometimes plays public service announcements (it is a public non-profit station) so soft it is hard to hear her or the PSAs. If I turned the music way up I am sure it would be fine, but it is not music intended necessarily to be very loud, especially as bedside music for relaxation.
Similarly when a BBC station I listen to switches between a program and the news on the half hour, the levels are so different it is sometimes jarring. This is compounded if the news reader has a soft voice. I love the soothing news voice of news reader Sue Montgomery on the BBC but if I adjust for her, but then a loud confrontational talk show like “Hard Talk” comes on, it can be jarringly loud (even though I like both programs).
Without “companding” everything to the point of keeping everything loud even when loud is not intended, there are compressors which can smooth out the peak levels or radio or the internet. But in my opinion these are not used often enough on some stations and networks. Just my $0.02 worth.
A final example refers to announcements on trains (commuter and subways). Some of these trains are noisier than others while running. In my experience (not all of it recent) the subways in NYC and Boston are much noisier that the subways in Atlanta and Stockholm. Likewise, in trains travelling between cities in the US, Amtrak trains are always much quieter than Metro North trains between the Hudson Valley and NYC. All are quiet when sitting in the station. So one can board nearly any train and may hear the destination and intermediate stops announced on boarding so a passenger can be sure he/she is on the right train. (Some also display the stops on a screen in the train.) But what is maddening is when a train starts, making loud engine and track noise inside the train, and a conductor or passenger enters from the next car letting in even more noise, but the conductor is trying to say “due to track maintenance this train will not stop at . . .” and is drowned out by external noise. The best solution, of course, is to build trains that are quieter for the passengers.
Enough about levels for today. Leave comments or ask questions if you wish. And come back often to TheAudioPenguin.com.