What is sound and how is measured in decibels
Acoustics is a field of physics that deals with the study of sound formation, its basic properties, and laws, as well as its practical application. As the application of sound evolved, so did acoustics as a science spread to various other areas of science and life in which sound emerges as a topic.
There is an intersection of acoustics with technology, that is, with industry, there have been links with many fields of engineering, especially those in the broader field of electrical engineering, and there is a combination of acoustics with non-technical sciences, such as medicine, psychology and arts.
What is sound?
The definition that is most widely accepted today and covers all forms is: sound is any time-varying mechanical deformation in an elastic environment.
Sound is produced when a change in the position of particles of a certain medium under the action of force occurs in an elastic medium. It is possible only in gaseous, liquid and solid environments, while there is no sound in a vacuum.
Sound generation and its propagation are phenomena in which air particles move from their equilibrium position under the influence of some force. The displacement of air particles is transmitted from one to the other, thus producing sound waves.
Sound source — the body that produces sound through its oscillation is called a sound source. An audio source can be anything that oscillates with frequency in the audible interval. From the sound source, oscillations are transferred to the surrounding particles. The particles oscillate to produce their alternating thickening and thinning — a sound wave. The sound wave in the ear causes the eardrum to oscillate, creating a sense of sound.
Sound wave — this is a mechanical wave motion that is created by mechanical oscillations in a material. Sound waves occur when a solid body vibrates. These vibrations move the particles of air around them. The number of oscillations (vibrations) in one second must be between 20 and 20000, to produce the sound that the human ear hears.
Sound waves can be spherical or flat. Spherical waves most commonly occur. The characteristic of these waves is that they propagate in all directions from the sound source. For flat waves, the oscillating surface is straight. Moving away from the sound source, the spherical wave transitions into a flat.
Sound field — this is the space where there is sound, mechanical disturbance.
Sound features:
- sound volume — depends on the energy transmitted by the wave (the higher the oscillation amplitude of the sound source, the stronger the sound);
- height — depends on frequency (number of oscillations per second; higher frequency = higher height);
- Color — characteristic of each type of sound, depends on the ratio of amplitudes and frequencies.
The appearance of sound in a person’s life is closely related to his sense of hearing, that is, to the fact that sounds causes an audible sensation.
That is why, in some circumstances, a subjectivist definition is used to say that sound is all that registers the sense of hearing. This definition is certainly incomplete because it does not include sounds that the human ear cannot perceive, nor does it explain its physical nature.
Sound is a physical phenomenon that forms an integral part of the human environment, where it occurs as an accompanying element of many life circumstances.
Sound is present almost everywhere, in the human organism, where speech occurs, through a variety of sounds present in the environment, to sounds in the depths of the ocean or the form of seismic waves reaching from the depths of the earth.
With such dispersion of emergent forms, the sound is a physical phenomenon that engineers of various professions are dealing with today. They observe and analyze it from different aspects and apply them in very different circumstances.
It is used by some areas of the arts as a means of expression (music, film, theater, radio, TV), which means for creative purposes. Sound is the basis of human communication, so in various forms of sounds, people find some sense.
According to the shape of the sound spectrum, the sound is divided into:
- Tone — which characterizes the periodicity of changes in the middle through which it spreads;
- Noise — which is non-periodic;
- Pure tone — occurs when the particles of the middle perform harmonic oscillations;
- Complex musical tone — created by the superposition of higher harmonics. A complex tone that we say is not musical has higher frequencies:
- Burst — represents a complex beep that suddenly builds up and disappears.
Sound volume and decibel
Depending on the frequency range, the audio signals are divided into:
Infrasound: 0 – 20 Hz
Audible sound: 20 Hz — 20 kHz
Ultrasound: 20 kHz — 1 GHz
Hypersound: 1 GHz — 10 THz
The sound volume can be:
Objective — energy that is transmitted by a sound wave in a unit time interval through a unit of surface.
Subjective — volume that is perceived by the sense of hearing. There is a connection between subjective and objective strengths.
For a sound wave to produce a sense of sound, it must have some minimum volume called the audibility threshold. The standard audibility threshold is assumed to be 1 kHz.
A person with a frequency below 16 Hz and over 20 000 Hz does not feel like sound at all. It is most sensitive at a frequency of 700 Hz to 5000 Hz.
The fact that the human hearing sense often appears in acoustics as a receiver imposes the need to adapt the way the state of the sound field is adjusted to the specifics of this sense. In engineering terms, certainly, the most significant feature is the logarithmic nature of its sensitivity. Such a characteristic is inherent in all the senses and is defined by the well-known Weber-Fechner law. Applied to sound and hearing, this means that at any value of sound pressure, it always takes about the same percentage of the change in condition to be subjectively noticeable.
Therefore, it is appropriate to use a logarithmic scale instead of a sound pressure scale to indicate the condition in the sound field. The logarithmic size that is widely used in engineering disciplines is decibel.
A decibel is, by definition, a logarithmic measure, but it is an indicator of the relay making an absolute scale in decibels for some physical size is possible if one of the two values in the expression is made constant and that value is predefined as a reference.
It becomes zero on a scale in decibels and every possible value is compared to the selected reference. It is on this principle that a new dimension, called sound pressure level, was introduced in acoustics.
The range of sound pressure values significant for humans is mapped to a range of sound levels in the range of about 0 dB to about 120 dB. On this scale, it is characteristic that a sound pressure of 1 Pa corresponds to a sound level of 94 dB.
From here, other characteristic values are easily recalculated, since an increase in pressure ten times corresponds to an increase in sound level by 20 dB.
Changing the sound level in decibels creates approximately the same subjective experience of volume change, whether it occurs in the area of quiet or loud sounds. As a result, the sound level as a magnitude suppressed sound pressure in engineering practice to representing the state of the sound field. All available instruments for acoustic measurements are marked in decibels.
The quietest sounds in a human environment are 20 dB in size, which is the realistic lower limit of sound levels in everyday life. The lower levels are only achievable with special measures of sound insulation, which is what is done when constructing studio spaces and concert halls. The level of 30 dB is considered to be sufficient “silence” for the bedroom environment in the apartments. Very loud sounds have order levels of 80 dB and above.
The maximum permissible noise level in an ambient environment for 8 hours is 85 dB. This is the limit value for working conditions. Exposure to higher sound levels at this time interval every day is thought to create permanent damage.
The sound level of concerts with sound systems is of the order of 90 dB or more, and the maximum sound levels in cinemas with well-tuned sound reproduction systems are up to 115 dB.
Sound protection and acoustic comfort
The appearance of sound in a human environment can be viewed from two aspects. The first refers to the sound that carries some useful information content. Such is the case with speech and music. The need in such circumstances is that such a sound should reach the listeners with as little degradation.
In the case of music, the sound received should, in some circumstances, satisfy some established aesthetic criteria.
Another aspect of sound observation concerns the need for people to protect themselves from the various sounds coming from the environment and not carry any informational content of importance, but they interfere with communication, concentration, disrupt sleep and the like. This aspect of sound occurs both in buildings and outdoors.
For this reason, a sub-area of acoustics was created, called sound protection.
Sound protection is a relatively broad engineering field that addresses the theory and practice of noise protection. The main topic of this field is the analysis of the passage of sound through different acoustic transmission systems in the human environment.
The goal of any such analysis is to provide in some way adequate noise attenuation before reaching potential listeners.
The great importance attached to ecology in modern times was reflected in the importance of sound protection in various fields of engineering: construction, architecture, transport, urbanism, mechanical engineering etc. The field of sound protection has been regulated over time by many laws and standards, establishing the obligation to deal with noise protection.
Finally, If you want to buy a pair of safe and comfortable headphones, then below is our list of recommendations based on quality, price and users’ feedback
For more information about noise cancelling headphones and headphones in general you might want to have a look at our list of e-books below
- Your health and headphones
- The In and out of anti-noise headphones
- Evolution of headphones technology
Related articles
Are noise cancelling headphones safe or dangerous?
Are noise cancelling headphones worth it?
Do noise cancelling headphones cause headache. Find out today
Do noise cancelling headphones damage ears and hearing?
High quality cheap noise cancelling headphones
These are major reasons why you need noise cancellation
This is why noise you need noise cancelling headphones when commuting
This is why you need noise cancelling headphones when in stadiums
This is why you need noise cancelling headphones when in the club
Top reasons why you need noise cancelling headphones when flying
Types of noise cancellation and why you need noise cancellation
What are noise cancelling headphones and how they work
The hidden truth behind noise cancelling headphones and vertigo
The shocking truth behind noise cancelling headphones and tinnitus
Five major reasons why you need noise cancelling headphones when meditating
Best noise cancelling headphones
Paww wave sound 3 active noise cancelling headphones review
Reasons why noise cancelling headphones are unavoidable when in the market
Sennheiser hd1 noise cancelling headphones review
Sensitive features to check before buying noise cancelling headphones
Sony wh1000 xm2 noise cancelling headphones review
Tao tronics active noise cancelling headphones review
The amazing science behind sound and music every headphones owner must know
The best headphones manufacturing companies and brands
The cause of hissing sound in headphones and how to correct it
The difference between wired and wireless headphones
The effects of dust to headphones you didn’t know
The history of headphones
The magic behind headphones wireless transmission technologies
The reasons behind the interference in wireless headphones
The science behind wiring system of headphones
The source and history of the word headphones
The theory behind how headphones work
Bose qc 35 noise cancelling headphones review
Components of headphones
Cowin e7 wireless active noise cancelling headphones review
Devastating side effects of high sound intensity to a human ear every headphone user must know
Discover the smartest way to keep your headphones clean and free from germs
Effects of water or sweat on headphones
Serious infections caused by sharing headphones everyone should be aware of