Noise

The first simple definition of noise I encountered many years ago was “Unwanted Sound”. And this is the definition I will maintain for the length of this page. 

Having been a physicist, chartered engineer and musician in the past, means that I know many more technical definitions However, it is the “unwanted” sound that annoys me. 

“Unwanted sounds” don’t have to be awful. I can remember the conductor André Previn arriving in London after a particularly turbulent flight saying that they played classical music as they flew through the turbulence. This music annoyed him more than the turbulence. 

Other apparently nice “unwanted sounds” are the carols they play in supermarkets as Christmas approaches. This is an awful distraction as I am almost tempted to join in and sing while I am shopping. 

Other really awful sources of “unwanted sound” include our favourite furniture store which insists on playing some sort of music through terrible speakers high up in the roof. The is VERY poor quality “unwanted sound”.

If you are unfortunate enough to have worked in any part of the Music business, it is difficult to ignore any sounds. Even active noise reducing headphones will cause our ears to listen even more acutely to the sound environment. 

The acoustical engineer who designed the Albert Hall “flying saucers” told me that his previous job had been designing “acoustic perfume” for cruise ships. He simply supplied sound through speakers in the cabins to mask the sound of the ship’s engine. He was using “noise”, as defined by scientists, to mask “unwanted sound” from the engines. 

https://en.wikipedia.org/wiki/Colors_of_noise

The URL above describes some of the scientific standard types of noise but we can create an unlimited number of noise types. “Acoustic perfume” would be one of these bespoke types of noise. 

So far, we have considered only relatively harmless “unwanted sounds”. 

It seems to me that the whole world has been growing increasingly loud. There is more traffic on the roads and some road users seem to enjoy making their engines louder. 

Most annoying is the fact that I do not see much attention being paid to the acoustics of restaurants and public places. The materials used in construction and flooring can make a place quieter with very little cost. If this is not done, we hear people shouting to be heard above the background sound. Then we ourselves have to shout to be heard. The result is a very high sound level but not usually permanently injurious.  

Probably the highest level sounds people will ever experience without ear protection are at pop concerts and gigs. The musicians at these events have their own small monitor speakers but the sound in various parts of the listening area can actually cause permanent harm to human ears. 

I can remember an occasion when, MANY years ago, I volunteered to help with the Noosa Jazz Festival in Australia. 

Click to access 2018-program.pdf

This is a wonderful opportunity to get up close with some remarkable musicians. I enjoyed every moment of it in the various cafés and restaurants around Noosa. 

The last night was a concert in the main auditorium under an open tent. But the sound level was so high that I could not approach nearer than about a hundred yards from the auditorium without feeling pain in my ears. I was very disappointed with this but I was VERY happy about the rest of the festival.

Years ago we dreamed of a system that could eliminate sounds that we did not like. Now that computing systems are so fast, some attempts have been made to do this with a remarkable degree of success. 

Simply put, a sound is composed of varying air pressures above and below our normal soundless air pressure. If we can simultaneously produce another sound which has the opposite pressures, going down when the original sound pressure goes above the normal pressure and goes up when the original sound goes below the normal pressure, we should completely cancel out the original sound. 

Unfortunately in the real world, the manufactured sound designed to cancel out the original sound will arrive a little late as the active system must use some clever but well-known mathematics to produce it. But already these systems are proving relatively successful in providing a useful reduction in the sound that a user experiences. Over the ear snug headphones are needed to experience this sound reduction.

There is no doubt that specially designed fast processors will provide an increased degree of active noise cancellation so that annoying “unwanted sound” can be reduced to a level of relative comfort with a pair of comfortable headphones. Carpe Diem!