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  Sound Levels

Can you believe the noise level rating published on the label?


We are often asked to recommend a quiet washing machine, dishwasher or fridge freezer or people will use the published dB ratings to compare different machines when in fact these figures are of little or no use.

In this article we will explain why you should not use these as a guide to how quiet or noisy an appliance happens to be.

  Short Version

The simple truth is that people often want appliances to run very quietly and, naturally assume that the dB rating to indicate noise levels of the machine given on the EU Energy Label will tell them this. Sadly, it doesn't and we will explain why in this article.

First we have to establish what is a Decibel? Well, just like watts for power, degrees for temperature or metres for distance, it's a unit of measure, but for the power of a sound, as opposed to electrical power, temperature or distance.

But, most importantly, it is not an accurate measurement in the same way as the more traditional scales of measurement to which we are all accustomed. noisy washing machine lady

Because of the nature of sound and the individual's perceptions of it, a decibel rating may seem louder or quieter to each person based on their own unique hearing. Different frequencies of sound will also seem louder or quieter from one person or another based on this fact.

So, for example, fingers drumming a table may have exactly the dB rating as fingers drumming a biscuit tin, yet the sounds are entirely different and one may seem louder than the other. So, the frequency of the noise also has a lot to do with how people think of a sound with higher frequency sounds typically seemingly louder and will agitate a person more that a lower toned noise at the same volume on the dB scale.

It is therefore a fact that there is no absolute scientific, quantifiable, measurement or standard by which to rate things on the decibel scale. The scale is meant as a indication of sound level.

Companies rate their products with a dBA rating which is typically compared to a rough charts shown in "The Long Version" below.

What this means that a dBA reading that you see on a product may or may not be accurate. Because its a comparison made in different setting than your particular application it will naturally be flawed from the very beginning.

To get your head around this think on it this way, if you walk across a room with a wooden floor and it's empty you get a hollow "echoing" type sound. But, in the same room, with furniture and curtains, perhaps a few pictures on the walls, the sound totally changes yet the flooring and walls are the same.

Sound characteristics change from room to room, where you site the machine, what's around about it to soak up noise and so on and all this means is that the dB rating that you see on the label or specifications, in the real world, is of very little practical use.

It is also well worth noting that some companies are more honest with their ratings than others. After all, how are you going to prove them wrong?

  Appliance Noise Level Comparisons

It is vital that you realise that trying to compare appliances based on the dB rating supplied does not guarantee that one machine will be quieter than another. This is why consumer testing, notably like Which? carry out, is subjective. The results are based on the decision of a panel of judges as measuring with a sound meter offers very little indication of how the machine will sound in the real world.

Due to this, basing your choice of appliance on, for example, the difference between a dishwasher rated at 33dB and one at 36dB would be at best a poor choice. You don't know how it will actually sound in use and you don't know how it will sound in your own kitchen, the rating simply cannot tell you this.

Also, given that these ratings are notoriously inaccurate only serves to compound the confusion.

  Long Version

The first thing that you have to remember when viewing the noise level ratings on any appliance is that they are tested under "ideal" conditions.

This means that they are installed correctly, if at all and that they are measured in a soundproof room with no reverberations, sound reflective surfaces or interference. In other words, conditions that you simply cannot replicate in your home.

The decibel measurement of sound which is abbreviated to dB is the unit used to measure the intensity of a sound.

The dB scale is a little odd because the human ear is incredibly sensitive. Your ears can hear everything from your fingertip brushing lightly over your skin to a loud jet engine. In terms of power according to the dB scale, the sound of the jet engine is about 1,000,000,000,000 times more powerful than the lowest audible sound. It's a big difference but, ask most people and they would not say that a jet engine is that magnitude of difference from almost total silence.

On the decibel scale, the smallest audible sound, almost total silence is rated at 0 dB. A sound 10 times more powerful is 10 dB. A sound 100 times more powerful than near total silence is 20 dB. A sound 1,000 times more powerful than near total silence is 30 dB, it's very confusing. noisy washing machine man

The fact is that the dB scale is logarithmic and not, as most people assume it to be, like most other scales of measurement, linear.

Here are some common sounds and their decibel ratings:

0dB - Almost total silence
15dB - A whisper
60dB - Normal conversation
90dB - lawnmower
110dB - A car horn
120dB - A concert or a jet engine
140dB - A gunshot or firework

From experience you will also realise that distance affects the intensity of sound. So, if you are far away, the power is greatly diminished and the noise, to your ear, is diminished. All of the ratings above are taken while standing near or, next to, the source of the sound.

In short the dB scale is, unless you understand it, very misleading if you think that 20dB is twice as loud than 10dB as, it doesn't work that way with sound. This also makes the system very hard to use in any practical way.

However, it gets still worse as you have conflicting yardsticks or references to use when it comes to sound levels in relation to the dB scale as another resource lists common sound levels as being:

10dBA - Normal breathing
20dBA - Mosquito or rustling leaves
30dBA - A whisper
40dBA - A bubbling stream, or a refrigerator
50dBA - Normal conversation
60dBA - Laugher
70dBA - Vacuum cleaner or hairdryer
80dBA - City traffic or a garbage disposal
90dBA - Motorcycle or lawnmower

Can you see the disparity between the two?

Which begs the next question, is "whisper quiet" 15dB, 30dB or somewhere in between? Is a normal conversation 50dB or 60dB? And, even if you establish that then how loud is the rating that you settle on in real terms? Then will the next person that walks into the room agree with your assessment?

It is therefore virtually impossible to use these ratings to compare different appliances.

  Noise & Environment

This is where we get into the practical application of dB and show that it is, in our opinion, a totally useless guide to noise levels from appliances.

The fact remains, that if you change the conditions or environment around the appliance you will change, at the very least, the sounds tone and pitch and, all too often, the actual volume as well.

As stated above in the example of the empty room, should you have a kitchen with a wooden floor, with laminate flooring on that then sounds will "echo" and can be enhanced. Yet use cork or real wood flooring and, depending on the characteristics of the flooring, it may "soak up" the sound, in effect, serving as a sound deadening.

From those simple examples you can see that the noise level that you actually get will depend entirely on where, how and on what you install the machine. In other words, the environment in which the machine is installed will have far, far more bearing on the sound level than the dB rating you see on the label. Even then, the rating on the label can tell you absolutely nothing about the pitch, tone or how long that volume is reached as well as, most importantly, whether YOU will find that sound intrusive.

But beyond that we've seen (or heard) cases where the appliances have been supposedly noisy only to find that the noise that has been presumed to be coming from the appliance was pots or crockery rattling in the adjacent cupboard, or on top of the machine, not the machine itself. This can often prove more irritating than the noise from the machine, the machine is fine the surroundings are not.

Once again, another example of the level of noise or pitch/tone and how much it annoys YOU often having a lot more to do with the surroundings than the actual appliance!

If you have read through the above you will see that we have established several facts about the dB scale:

  • It is not a linear scale
  • It is unreliable
  • The references are flawed
  • The installation of the appliance can affect sound
  • The actual sound, the noise you hear can vary in pitch and tone yet remain at the same rating on the scale
  • The surroundings massively affect the sound in tone and intensity
  • The measurements given are often unreliable
  • The measurements are made under "ideal" conditions

When you look at this there is a lot of call to simply draw a line here and reach the conclusion that this is a waste of time and that the dB ratings on appliances as a guide to noise level are meaningless and, you would be correct.

Presumably the published figures should help us to decide between the models of the same manufacturer, as the conditions of measurement should be the same. For instance it might help us decide whether to pay half as much again for another model.
simon taylor
I'm a professional noise and vibration expert and I'm sorry, but there is some nonsense in this article.There is some true stuff, and I appreciate the sentiment, but nonetheless a fair bit of nonsense is spoken.The issue is that there is no British Standard (BS) for measuring these pieces of equipment. That is all. To suggest it is impossible to do so, is wrong.
Kenneth Watt
There is no maximum or recommended noise level, largely for the reasons explained above.
I have a noisy fridge, the company claims its normal - we can't hold a conversation at the kitchen table, and at night we hear it in the bedroom. How can I find out what the maximum allowable noise for a kitchen fridge is.Micah
Kenneth Watt
Not really no.One at 40dB might have a squeal. One at 45dB might not. Completely different sound characteristics and ratings with the "supposed" quieter one actually proving more noisy or irritating to the user.
I understand the point that perception is variable and local environment also affects noise perceived in reality, but surely this is still a good scale to compare machines to each other.My washing machine will always be in the same room, so whatever model I choose it will have the same environment and the same people listening to it. So I can reliably believe a 40dB rating will be quieter than a 45dB. No?

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