Appliance noise - what you didn't know about decibels

Loudness and decibels

You must have heard or read many times that a certain appliance, machine, voice, animal or any other source of sound emits a certain number of decibels. For example, there are also various government regulations setting limits on noise under certain conditions. Do you think 29 dB sounds like quite a lot of loud sound, or, conversely, not loud enough? Without context and further knowledge, it is hard to imagine what the loudness actually is.
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Decibels are a more complex unit of measurement than they may first appear. Let's at least get some clarity in this area.

A little bit of physics

In order to understand the principle of loudness measurement, it is necessary to look at this issue at least marginally and simplistically from the point of view of physics. Don't be alarmed, you don't necessarily need to read this section, but it will be fundamentally helpful in understanding the issue of sound and decibels. At its core, it is not something completely incomprehensible.
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> Sound propagates in waves. These waves carry energy that increases with frequency (i.e. pitch) and with amplitude (i.e. volume). However, the dispersion of sound waves in space is also important for human hearing. Therefore, even though in-ear headphones sound much quieter than, for example, large speakers, they can be much more dangerous to a person's hearing because all the sound propagates directly into the eardrum. Due to the miniature surface area of the eardrum (about 50 mm2) and its internal part that processes sound waves into a signal that can be read by the brain (about 3 mm2), only a tiny amount of sound power is needed to pack huge amounts of sound intensity into such a small area.

The sound intensity is calculated as: I = P/S	I ... sound intensity (W/m2)
	P ... sound power (W)
	S ... the area through which the sound waves pass (m2)

Sound intensity is defined by the ratio of the power of the sound wave and the area through which the wave passes. In the context of human hearing, this quantity can take on very unintelligible values over a large range. The threshold of audibility has a value of 10-12 W/m2, or 0.000 000 000 001 W/m2. The threshold of pain has a value of 1 W/m2. As you can see, the range between these values is huge and quite opaque. This is why the decibel unit was created.

Audibility threshold: the lowest level of sound that the human ear can detect.
> Pain threshold: the value of sound intensity at which a very painful sensation is produced. A high level of pain at which hearing damage is likely to occur.

"Audibility threshold	Pain threshold
10-12 W/m2	1 W/m2
0 dB	120 dB

Decibels are a derived unit that was introduced primarily for clarity of sound loudness measurement, especially in the context of human hearing. It is a unit with clearly defined ranges, where 0 dB represents the audibility threshold and 120 dB the pain threshold. This is a more understandable expression of the intensity level of sound, since most sounds in our everyday life find their intensity value in this range. But how is this range of values achieved?
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> The Decibel is not a common unit such as the kilometer, kilogram, etc. It is an expression of the ratio of two values on a logarithmic scale. The calculation of decibels is done as follows:

L = 10 * log10 (I/I0)	I0 .... audibility threshold
	I ... intensity

The decadic logarithm is a function that tells us what number to multiply ten by to get the argument, the number in parentheses. This method of conversion reorients the sound intensity values into clearer values. However, it has its pitfalls.
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The main weakness in understanding decibels as a unit is the logarithmic scale just mentioned. Since decibels are an expression of the intensity level of sound in a logarithmic function, it cannot be said that, for example, 20 dB is twice as loud as 10 dB, as perhaps most of us would expect. In fact, a 10 dB increase is ten times the noise. A 20 dB increase is then a hundred times the original noise, a 30 dB increase is a thousand times, and so on. This is principle of the logarithmic function.

Negative decibels are of course possible. However, these are sounds of an intensity that human hearing cannot detect. For an example, see interesting facts below.

Sound Source Comparison

Now enough physics and decibel sauce. Let's take a look together at a practical comparison of sound sources. Of course, the comparison won't miss our quietest refrigerator on the market, the Lord C15.
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-------------------- Audibility Threshold: 0 db ---------------------

Quiet breathing: 10 dB
Leaf noise in light wind: 15 dB
Quiet garden: 20 dB
Lord C15: 29 dB
Whisper: 30 dB
Light rain, muffled call: 40 dB
Normal speech: 60 dB
Vacuum cleaner: 70 dB
Heavy city traffic, shouting: 85 dB
Moving train: 90 dB
Music in headphones at highest volume: 95 - 110 dB
Annoyance threshold 105 dB
Rock band: 110 - 120 dB
Aircraft taking off: 120 dB

---------------------- Pain Threshold: 120 dB --------------------

Starting gun, fireworks: 140 dB
Rocket launch: 180 dB

Sound intensity of 150 dB and higher can destroy eardrums. You should stay away from sources of such intense sound or use appropriate protective equipment. Sounds of 85 dB and above that affect a person's hearing over a long period of time can be considered dangerous and can damage hearing. For example, prolonged listening to music with headphones at maximum volume can lead to very unpleasant hearing problems such as tinnitus, which manifests itself as whistling in the ears.

Interesting facts from the world of sound

Sound in a vacuum?
For sound to propagate, the environment must contain some particles. If the environment does not contain particles, sound cannot propagate via waves. A vacuum does not contain any particles, so sound does not propagate at all in a vacuum. Therefore, there is simply no sound in the vacuum of space. Yet sound is observable in space. But that is another chapter and would require going into more detail.
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Speed of sound
The speed of sound in air is approximately 340 m/s. In water, sound waves have a speed of 1500 m/s, which is almost 4.5 times faster. The speed of sound depends on the density and elasticity of the material. Sound travels faster in liquids and solids than in gases.
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The loudest animal
The record holder from the world of fauna is the whale, specifically the sperm whale. The sound of these amazing creatures singing can spread hundreds to thousands of kilometres underwater, and its volume can reach up to 230 dB. By comparison, the African elephant's trumpet is approximately 115 dB.

Surprisingly loud little guy
Representatives of the animal kingdom that you probably wouldn't expect to hear such values include shrimp. This little creature can make sounds of up to 200 dB.

The loudest sound in human history
The eruption of the Krakatoa volcano in 1883 was heard over approximately one-third of the entire globe, and the sound wave circled planet Earth a total of 3.5 times. The sound intensity level was 310 dB.
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The quietest place on Earth
The quietest place on Earth is the research chamber at Microsoft's US headquarters. The measured noise level here has been set at -20.3 dB.

Noise level of appliances

We are Lord, manufacturers of quality and honest appliances. We are committed to providing our customers with first-class products that meet all expectations. One of these expectations is that they will not interfere with the everyday comfort of the home. Silence is, although it may not seem like it to some, an important attribute of an appliance.

With quiet appliances, you will be able to afford a better rest, you can have a more pleasant home environment, or if you work at home, a work environment. If you have a small child, you don't have to worry about waking them up with the hum of the washing machine, for example.
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One of the proofs that we are serious about quiet appliances is the Lord C15 refrigerator.

Our Lord C5, the quietest fridge on the market

Lord C15, the quietest refrigerator on the market. In terms of noise level, the Lord brand refrigerator is the throne among these appliances. The extremely reliable, economical and elegant refrigerator gives you exactly what you need. As a bonus, it won't disturb you under any circumstances, even if you have a bed in the same room.
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The Full 5-year warranty guarantees that perfect performance is maintained. The 5-year warranty is a clear signal that we trust our products. You won't just get rid of this appliance, it will last you for ages. And you'll be very glad you did.

Learn more about the Lord C15 and discover the definition of total silence without distractions in your home.