Webster’s New World Dictionary describes noise (noiz) as “a din of voices; clamor, or any ‘loud, disagreeable sound.’”

Wikipedia notes that “in common use, the word noise means any unwanted sound.” In relation to sound, noise is not necessarily random: “Sounds, particularly loud ones that disturb people or make it difficult to hear wanted sounds, are noise.” For example, conversations of other people may be called noise by people not involved in any of them; any unwanted sound such as dogs barking, neighbors playing loud music, portable mechanical saws, road traffic sounds, or a distant aircraft in quiet countryside, is called noise.

Acoustic noise can be anything from relatively quiet, but annoying, to loud and harmful. At one extreme users of public transport sometimes complain about the faint and tinny sounds emanating from the headphones or earbuds of somebody listening to a portable audio player; at the other the sound of very loud music (even from headphones or earbuds), a jet engine at close quarters, etc. can cause irreversible hearing damage.

Here are a few sounds that the Journal of Neuroscience notes are the most universally annoying:

1. Knife on a bottle
2. Fork on a glass
3. Chalk on a blackboard
4. Nails on a blackboard
5. A female scream
6. A disc grinder
7. Squealing bicycle brakes
8. A baby crying
9. An electric drill

From the complaints I have heard over the years, I can add:

1. A nearby “boom car”
2. A car alarm
3. A car or motorcycle with a modified exhaust system
4. Loud musical entertainment
5. Dog barking/howling
6. Just about anything unnatural – particularly at nighttime.

Our experience is that sound is more likely to be perceived as noise when it is “unnatural” to the surroundings and pervasive (or intrusive). Pure tone sounds are considered more annoying than broadband noise, and many ordinances apply a 5-10dB “penalty” for such sounds to normal limits. Impulsive sounds, like a door slamming, may cause high levels, but for an instant, and many ordinances allow for this.

NOISE MAY ONLY BE IN THE “EAR OF THE BEHOLDER”

Noise is perceived differently by different people, based upon their history and environment:

• Those accustomed to quiet, rural setting, may find city traffic very annoying, while those accustomed to city life may find a rural environment “too quiet” and disturbing.
• People who are part of a celebration or similar event may find loud music “invigorating,” while those outside the area may find it objectionable.

During my nearly 40 years doing noise measurement and remediation, I have come across numerous instances where only one person can hear a certain sound, or be bothered by it. As an example, a man in northern New York was awakened every night by the sound from a mine ventilation fan two miles away. The sound at his property line was only 28dBA. As it turned out, he was a retired volunteer fireman, and the sound from the fan was the same frequency as the fire siren to which he was conditioned to respond. (The mine officials agreed to change the fan by slowing the speed and adding more blades, thus shifting the frequency without sacrificing airflow.)

In another New York village, a rooftop exhaust fan on a diner is annoying only one family, whose residence is located on a hill overlooking the diner. In this case, the combination of a pure tone source, and modulation of the tone caused by two like fans operating together, creates an extremely annoying condition. Although noise from the highway can, at times, be louder then the fans, the fan noise is continuous and pervasive. It can be legitimately argued that the noise is necessary to the operation of the diner, and that it must continue well into the night to coincide with the diner’s operating hours. But is it “excessive”? Yes, when it can be heard inside the residence at 2 AM with the windows closed. The court agreed, and ordered the diner to remediate the problem.

Residents of a North Carolina community are upset about the “noise” emanating from a nearby church. Although the rock music may be considered a “necessary” part of the church service, it surely must be considered “excessive” when it can be clearly heard inside residences hundreds of feet away. In situations like this, controls must be placed upon the sound intensity, the amount of bass, and the days and times when the activity is allowed – irrespective of what might be stipulated in an outmoded noise ordinance that fails to recognize the annoyance posed by pulsing low frequency sound.

WHAT MAKES NOISE “ACCEPTABLE”?

Which leads us to ask: “Why is some noise ‘acceptable’- and some not? Why are certain noises ‘exempt’ from regulation? Should not all noise be treated the same? Yes and no.

The only criteria that should be used in judging whether noise is allowable:

• Is it necessary? Sounds generally considered necessary are safety or security alarms, emergency vehicle sirens, noise from construction and maintenance services, noise from traffic, and the like.
• Is it modest or excessive? This relates not only to the intensity of the sound, but also its duration and timing.

As I write this article, I hear a rather annoying buzz from a nearby large lawnmower. Is it necessary? Yes, if we want the grass mowed. Is it excessive? Not really, because, even though the level is well above 80dBA near the mower, I measured only about 55dBA in the office and know that it will only last for ½ hour or so, will never start before 8 AM, and will almost always be on Wednesday morning. We can, as they say, live with it and, if need be, work around it. (Right now, I’m going for a walk, because I can’t concentrate with the noise coming from the lawnmower, leaf blower and hedge trimmer.)

But what happens when necessary noise is excessive – beyond what it needed to obtain the desired results? With the lawnmower, not much can be done beyond making sure that it has a good muffler and limiting the exposure time. With highway traffic, exposure can be reduced with the erection of noise barriers – the construction, height and width determined by the anticipated noise levels and distance from either the source or the receiver.

Although many ordinances set objective levels of noise at a source or receiver property line, the stipulated levels are often expressed in “A-weighting” – which unfortunately fails to address the annoying effects of very low frequency sound that can be generated by modern sound systems. When many of these ordinances were first penned, there were no “boom cars” and the best sound systems had speakers with 12” diameter paper diaphragms that barely went down to 50Hz.

Now, we have systems that can produce digital sound into sub-audible frequencies – sound that goes through walls as if they were paper – sound that travels for miles (and can annoy blocks away). Outdoor entertainment venues are particularly problematic, particularly when the person on the “sound board” is (as most are) inexperienced – or unconcerned. Fortunately, new digital mixers allow peaks in volume to be “clipped” and very low frequencies to be selectively removed.

TYPICALLY EXEMPTED NOISE SOURCES

Many noise ordinances exempt certain types of noise, such as that generated from construction or repair activities, emergency service vehicles or even church bells, the latter exemption sometimes being perverted to justify excessive sound from religious activities as a First Amendment right.

Should unwilling people be exposed to annoying sounds simply because they come from an exempted source? The answer, in my opinion, is a resounding NO! Noise is noise! Even sounds which are considered “necessary” should be controlled to as low a level as is physically and economically feasible – consistent with the intended purpose.

Robert Andres is a Certified Safety Professional, Fellow of the American College of Forensic Examiners, and a member of the Institute of Noise Control Engineering. He is a Clarkson University graduate with over 40 years experience in the field of noise measurement and control. The founder of Oshex Associates, Inc., Syracuse, New York and principal of Environmental and Safety Associates LLC, Naples, Florida, he serves as Technical Advisor to Noise Free America: A Coalition to Promote Quiet.