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Room Noises


Room Noises

There I was the other night, sitting back and relaxing, listening to some new Manger speakers, fully entranced and enthralled when the cuckoo clock went off. Yes I do actually have one but I had forgotten to turn it off before settling down for a listening session. It made me think of the relationship between our hifi equipment and the room environment.  We spend a lot of money, time and effort to obtain the best possible sound from our gear but how much time do we actually spend on the room?

With so much effort to reduce noise floors of equipment, high-grade cables, lower distortion figures and the like, it seems strange to have so much noise possibly ruining our listen experience. Our ears and minds are very good at filtering out and ignoring unwanted noises but the less they have to filter, the easier and better the listening experience will become.

Background noise is interesting. The ticking from the clock I was completely oblivious to, probably from being so used to it but every half hour the bird pops out and sings its little song. Because that noise is fairly infrequent it is hard to get used to. This applies to other background noises like trucks going past, motorbikes, children playing etc. Making these noises go away can be quite difficult. Okay I can turn off my clock but to silence the kids may be a bit harder and the truck, well that would probably need double-glazing and a thicker front door. While neither inexpensive nor simple, it is certainly something to consider for those ultra-high-end listeners who have the budget. A side effect is that it will help reduce your heating and cooling needs hence less air-conditioner noise. Many people even build specific rooms for listening and these are usually fitted out with soundproofing during construction.

Many devices can make noise as well, such as hums and buzzes from fans, heaters, fish tanks and the like. During the time period you usually listen to your hifi, sit down with your hifi turned off and make a list of the things that make noise. One by one try and see what can be done. Certain devices may be able to be switched off; sometimes you can connect them all to the same power board and then one switch will help you create silence. Otherwise some items could be moved to another room or further away. Replacing that old heater with a new one such as a silent heater panel can stop that fan noise once and for all! Things like fish tanks cannot be switched off so consider moving them to another room or hunting down pumps and bubblers that are as quiet as possible. Isolating mechanically noisy devices on rubber pads or blobs of sticky tack can help as well.

The next step is to then listen to the sound the equipment makes. Turn it all on but have nothing playing. Most of the time everything should be silent, a few larger amps or even smaller ones may have fans built it but otherwise no noises should be heard from your listening position. Power transformers may make a very slight hum, usually only heard if you listen very closely. If you can hear it more than about a metre away, there may be a problem. Listen to the speakers and gradually increase the volume. All equipment produces background noise and the noise will likely increase slightly. However when the volume control is at or above normal listening position, you should still have very low noise levels. If it is too loud, check for earth loops or ask you dealer / manufacturer for advice. Generally the lower end the equipment, the noisier it is. Valve gear can also tend to be a little noisier than solid-state equipment.  

Another very good exercise is to play a test disc that has a full frequency sweep. Make sure you pay attention to the instructions on the liner notes as some of these can contain very high level signals but they are excellent at finding things in the room that vibrate. At the lower frequencies (you may need to use the CD player’s repeat function) it is likely windowpanes, cabinets and other objects will start to vibrate as they resonate with the sound. Move around to each item and see if screws can be tightened, things adjusted or moved in such a way that the resonance is reduce or stopped. Window frames may need professional adjustment but sometimes an easy fix is to jam something between the frames.

Weights or sheets of deadening material can be attached to large surfaces that vibrate, for example the back of a bookcase or a picture frame. Make sure you retest with the frequency sweep as it may have not been enough, adding dampening usually reduces the resonance frequency lower but you may need more. One area that may require professional help is the addition of dampening sheets to the inside of hifi equipment. Tap the lid of your gear and see what you can hear. Well made products will sound dead however many wont and will ring and vibrate. Sheets of deadening attached to the inside will help this but seek help if you are unqualified to modify it yourself.

Once you have completed this exercise, you will have lowered the total noise floor of the room, something akin to the signal to noise ratio of the hifi gear itself. Frequency dependant vibrations should have been reduced or even removed. Keep in mind it can be very difficult to remove all noises and vibrations, but even a reduction is time well spent. All this will add to an improved listening environment and of course more enjoyment for you the audience.

Written by Leon Gross, originally published in Audio & Video Lifestyle magazine.