What is sound: an introduction to sound waves

Sounds are mechanical oscillations that impact the auditory organ, and in this essay, we would like to introduce you to some fundamental concepts that will help you better comprehend these phenomena.

You may not recall the physics classes in which these concepts were discussed in greater detail, therefore we will summarize these concepts in a concise manner. We will discuss sound waves, sound, its many forms and features, all of which are aspects that you may meet in everyday life, particularly if you are in the market for an audio system. However, let us begin sequentially:

What exactly is acoustics?

Acoustics is a branch of physics concerned with the characteristics, generation, and transmission of sound. In other words, it is a science of sound that encompasses all of its facets.What is sound: an introduction to sound waves

There are several subfields under this extremely broad science, including physical acoustics, electro-acoustics, technical acoustics, space acoustics, musical acoustics, phonetics, and audiometry.

What is audible?

Numerous sound sources are capable of generating mechanical waves that impact the human auditory equipment, the ear, which may provide an answer to the issue of what sounds are.

Additionally, sound may be defined as the feeling produced by sound waves on the auditory organ via vibrations. Additionally, sounds are musical vibrations or components of speech.

What is sound is the response to the question. It can be rather complicated, but the important thing to remember is that it relates to the vibration or oscillation that the human ear can detect.

Apart from the nice sounds that you may detect, such as music, nature, and human voice, there are also a variety of noises known as noise pollution that can be rather unpleasant and pose a serious problem, particularly in large cities.

What are the sources of sound and how do they spread?

We can refer to these as sound sources, or bodies capable of emitting sound under specific conditions.

However, what are the noises and how are they generated? Vibrating strings: voice cords, instrument strings, etc. ; vibrating air columns: wind instruments, organs, etc., sound tubes; vibrating membranes or plates: percussive instruments, speaker, etc. I chose these instances because they are more convenient and well-known, but there are undoubtedly many more.

After being emitted, the sounds must travel from the source to the receiver, a process known as sound propagation. They disperse in a variety of ways depending on the environment in which they are released (gas, liquid, solid).

Typically, you will utilize sound propagation outside and inside, and by understanding the characteristics of air, you will be able to do numerous calculations to appropriately design the audio system in the event of a requirement.What is sound: an introduction to sound waves

Thus, sound waves propagate in the open air in the shape of a sphere, both longitudinally and transversely, as a mere transfer of energy devoid of substance. The energy diminishes as it goes away from the source until it is totally lost. The echo is a regular occurrence in nature. It is the reflection of a sound generated in nature that hits an obstruction and returns as a separate sound from the original.

Indoors, the situation is entirely different; sound waves generated by a source encounter barriers before attenuating; the sound field is not spherical as it is in the open air, but rather depends on the room’s geometry and acoustic characteristics.

What qualities does the sound have?

To help you better grasp the concepts, we will also discuss the properties of sound, which we will provide below.

Frequency of sound

The perceived frequency of sound might be low, medium, or high. It is expressed in hertz (Hz) or cycles per second and is defined as the number of phases or oscillations occurring during a certain time period. Although these sound waves may propagate at both high and low frequencies, the human ear is only capable of perceiving a limited range. In a variety of settings, sounds can be created at the required frequency.What is sound: an introduction to sound waves

Intensity of sound

It is expressed in decibels (dB) and is present in a wide variety of home items. The lowest intensity heard by the human ear is regarded to be 0 dB, whereas the breath of a person next to you or the rustling of leaves is thought to be 10 dB, and whispers are considered to be 20 dB.

The sound scale is logarithmic, which means that the noises created by whispers are perceived as being ten times louder than the rustle of the leaves. When you are outside, meteorological variables such as temperature, air pressure, and humidity all affect the intensity of sound waves.

On the other end of the spectrum are high-intensity sounds, which occur when sources are close to the receiver and have an output of 80 dB from a vacuum cleaner or 120 dB from a rock concert. At 130 dB, it is considered a threshold; anything higher than that might induce pain.

We may divide this feature into two categories: sound intensity and auditory intensity. Thus, the initial intensity may be adjusted to suit each individual’s preferences. It is a quantifiable objective quantity, in contrast to auditory intensity, which is a subjective assessment unique to each.


Volume is a property of sound that you will perceive. We can refer to the maximum distance traveled by a wave from point 0 as its amplitude (of the source). Additionally, it is defined by the degree of movement of the air molecules; as the wave expands, it strikes the hearing aid with increasing force.

Sound velocity

The speed of wave propagation is dependent on a variety of factors, and a suitable environment is required for them to be transferred from the source.

If we refer to the sound speed in the air, it is dependent on the following:

– air pressure: increasing in compression zones and decreasing in rarefied places;

– air temperature: on hot days, the speed is greater than on cool days;

– humidity: when the humidity level is high, the speed rises.

The speed of sound propagation in air may be readily estimated using the following mathematical formula:

Sound speed = 331 meters per second plus 0.6 (for each degree C).

In other words, at 0 degrees Celsius, the speed of sound is 331 meters per second. Each extra degree raises the speed by 0.6 m / s.

The speed of sound in a vacuum is zero, as it lacks an environment in which to propagate. Since 1660, several tests have been conducted to establish this truth.

The propagation medium is also critical, as it travels at a speed of 331 meters per second in air at 0 degrees Celsius; 1482 meters per second in water at a temperature of 20 degrees Celsius; 3850 meters per second through oak wood; 5000 meters per second through iron; and 5640 meters per second through glass.


Another property of sound waves is their wavelength, which is mathematically connected to their speed of propagation and frequency.

The electromagnetic spectrum is split into wavelengths, with radio waves at the top, microwaves, infrared, visible light as a medium, and ultraviolet, X-rays, and gamma rays at the bottom.

Thus, if we consider a simple sound, such as a musical note, we can describe it in great detail using three perceptual characteristics: pitch, which has a frequent correspondence; intensity, which refers to the harmonic constitution of the waveform; and timbre, which refers to the harmonic constitution of the waveform.

On the other hand, noise is far more complicated, and the sounds are not harmoniously connected, resulting in the sensation of discomfort and tension.

Frequency-based classifications of sounds

We have many sorts of noises based on their frequency, and we may discuss ultrasound and infrasound, each with its own unique characteristics.

Ultrasounds are those that create a frequency greater than the human ear’s maximum perceptible frequency (between 20 kHz and 10 at the power of the 6th kHz). They are invisible to humans, they contain a great deal of energy, they can also take the shape of a beam, and they perform very well in gaseous settings, where they are powerfully absorbed.

They have a broad variety of uses, including those in medicine, technology, and nature. Thus, metal components can be cleansed, metals can be chopped, and they may be used to create certain serums and vaccinations, sterilize, preserve food, identify items and relief forms in the aquatic environment, and so on.

When comparing infrasound with ultrasound, the former is on the other end of the spectrum, being undetectable to the human ear yet occurring between 0.001 Hz and 20 Hz. It is worth mentioning that it is possible to travel extremely long distances without losing intensity, allowing for the possibility of avoiding obstacles without incurring significant losses. As a result, they are critical in the area of seismology, as they enable the study and prediction of earthquakes.

Thus, when it comes to sound perception, ultrasound and infrasound do not fall inside the audible range, and the human ear cannot tell them apart. However, investigations have shown that, even if the ear does not detect these sounds, they nonetheless generate states that the listener cannot explain. During a performance, songs with 17 Hz infrasounds were played, and some audience members experienced anxiety, panic, even terror and rage.

How does the human ear develop?

The sound wave in the human auditory system is longitudinal in form and travels across all sorts of surroundings.

We take a brief look at the components of the human ear and the physics equivalents for each component:

– the ear flag, which is comparable to an acoustic trumpet;

– the ear canal is shaped like a tube with one end closed;

– the eardrum is a semi-permeable membrane;

– the middle ear serves as a resonator and also serves as an amplifier of sounds;

– the inner ear might be irritated

What is sound: an introduction to sound waves

In which sector is it possible to apply knowledge of sound waves?

If you are not active in the area of music, or in the design and building of a concert hall with basic acoustics, or if you are not a sound engineer, etc., you are probably wondering when you will need this information.

You will be able to use these concepts when purchasing an audio system for your home, speakers, or a sound amplifier, allowing you to comprehend the manufacturer’s data and make an informed choice.

For an audio amplifier, it is critical to have information on the amplifier’s power, with a focus on real power, not maximum power; frequency band, taking into account the interval perceived by the human ear; and impedance, which must be matched to the speakers’ impedance.

While you are probably familiar with the concepts provided in the article, you may have forgotten what they represent. Do not hesitate to read attentively in order to refresh your memory. There are physics-related aspects, but they also have application in everyday life, enabling you to make sound judgments and comprehend specific occurrences that you may face regularly.

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