An oversimplified two-dimensional Good-Good vs Bad-Bad Matrix about Sound and its Quality.

By a very simple definition, an unwanted sound is referred as noise. While the definition is complete, it still is too short to get the real understanding of what noise is. Hidden is a subjectivity factor of the word ‘unwanted’ making a proverb, “one man’s music is another man’s noise” all the more relevant.

To be really over-simplistic – Sound constitutes of two important aspects Quality and Quantity. While the latter is easier as it is measurable in various units, the former poses a bigger challenge. How sound is perceived by a measuring microphone and how it is heard by a human ear (and mind) could be very different. This has given rise to the whole new stream of acoustics called ‘psychoacoustics’.

Most of the endeavour is in the direction of correlating these two measurements and trying to get some sense that is relevant to our hearing through measurements.

When even ‘good quality’ sound gets too loud in quantity it becomes annoying and noisy. We see this phenomenon very often during festivals where the music is played at excessively loud levels. And if the sound is unpleasant and random, the woes are multiplied; ask the people living near airports or railway lines. Very loud noise just surging without any notice – this is the height of annoyance.

Well, there are always the exceptions where too much of silence can be ‘deafening’ and sending an individual into depression and on the other hand there can be an individual who is very much liking the noise and the ’life’ all around him! At times, brain plays weird games with those (for example) living near airports and railway tracks. Over the time, these people become selectively deaf to the aeroplane and trin noise but are perfectly sensitive to the other noise! But then those are exceptions and are out of the purview of this article.

To explain how low intensity but bad quality of noise can be irritating, I had a client many years back who lived near sea-shore on 18^th floor. And he had peculiar problem with the public transport buses having stop-start acoustic bells. The traffic made noise too, but it was constant like a static noise floor and thus though being high in quantity didn’t bother him due to its characteristic. Even honking was almost constant during the day at reasonable intervals and absent at night. But the low noise of public transport bell annoyed him and woke him up from the sleep as it was random and having sudden impact out of nowhere.

Then the strange fact emerged as we spoke more at length. It was revealed that it closely resembled with the prayer bell that he had in his house in his childhood. Now there was an association established and his mind just woke him up every time the bell rang! It remained annoying till the room was not treated to some extent. Quite strange the way our brain works and interprets the sound and other stimuli!

However, most of us are in the region of high intensity and bad quality industrial noise exposure, especially during the daytime and many of us even during the night-time. We, unfortunately, have to keep the doors and windows closed for achieving decent levels of noise attenuation – compulsion of air conditioning, thus, is not just restricted to temperature regulation.

Further, the biggest leakage points need to be plugged. The air gaps in the doors and windows (when they are closed) are the biggest next source of noise leakage.

Since we live in a country where most of the walls (even the internal ones) are made of brick and mortar (unlike US where drywall construction is common), it is the quality, thickness and weight of our doors and windows that determine the next level of noise leakage. Once these are of good quality of hardware and installation, the walls themselves are the next culprit.

The walls then need to be layered with low sound transmission materials end-to-end. More are these layers, better is the insulation and isolation. And finally, there still would be some noise that will make it through. This needs to be absorbed through absorptive surfaces so that it diminishes on various surfaces before it reaches listener.

I admit that treating the room like this is expensive and it needs special expertise and consultation. Another issue in most of the client’s mind is that the room becomes considerably smaller due to this treatment. Put the factors together and a strong resentment arises – the client who can spend on soundproofing is a wealthy one and he is bound to have expensive real estate!

The bare necessity of having a quieter home then gets reduced to treating only the AV room as a special consideration.

With nice mild lighting, cushy reclining chairs, silent air conditioning and silence at its best within the house; I’ve had clients whose children want to have their afternoon siestas and homework session in the AV room! It’s the cosiest!

– By Mehul Mepani