The speed of sound is a fundamental concept in physics and acoustics that is of great importance in various fields of knowledge.
This article aims to examine in detail the speed of sound, its definition, its influencing factors and its applications in a variety of scientific and technological disciplines.
Definition and concept
The speed of sound, denoted as "c", is a magnitude that represents the speed with which sound waves propagate through a given material medium. It is an intrinsic property of said medium, and its value varies depending on the characteristics of the latter.
In a homogeneous and isotropic medium, such as air at a standard temperature and pressure, the speed of sound is around 343 meters per second (m/s). However, it is important to note that this speed can change significantly depending on various physical and environmental factors.
Factors that influence the speed of sound
The speed of sound in a given medium is determined primarily by three key factors:
1. Density of the medium
The density of the medium through which sound propagates is a fundamental factor in determining its speed. In general, in denser media, such as solids, sound travels more rapidly than in less dense media, such as gases.
This is because particles in a dense medium are closer to each other, allowing for more efficient transmission of sound energy.
2. Elasticity of the medium
The elasticity of the medium is another determining variable. Elasticity refers to the ability of the medium to deform and recover its original shape after a disturbance.
In elastic media, such as solids, particles can vibrate more easily and therefore sound travels faster. In contrast, in less elastic media, such as liquids and gases, the speed of sound is lower.
3. Temperature
The temperature of the medium also has a significant impact on the speed of sound.
At higher temperatures, the particles of a medium have greater kinetic energy and therefore vibrate with greater amplitude. This leads to a faster speed of sound in hot media. On the other hand, at lower temperatures, the speed of sound decreases.
4. Pressure and humidity
The pressure and humidity of the medium can affect the speed of sound, although their influence is minor compared to the previous factors. Under high pressure conditions, such as deep in the ocean, the speed of sound can increase slightly.
Humidity, for its part, can alter the speed of sound in air, although these changes are usually small and less significant than the effects of temperature and density.
Examples in different conditions
Below is a table with examples of speeds of sound in different media and conditions.
|
Half |
Speed of sound (m/s) |
Speed of sound (km/h) |
|
Air (20°C) |
343 |
1235 |
|
Water (20°C) |
1480 |
5328 |
|
Steel |
5000-6000 |
18000-21600 |
|
Oak wood) |
3300 |
11880 |
|
Concrete |
3200-3600 |
11520-12960 |
|
Glycerin (20°C) |
1920 |
6912 |
|
Helium (20°C) |
965 |
3474 |
|
Glass |
4540 |
16344 |
|
Diamond |
12000 |
43200 |
|
Oxygen (0°C) |
316 |
1137 |
|
Hydrogen (0°C) |
1280 |
4608 |
The speeds in the table are approximate and may vary slightly depending on specific environmental conditions.
As can be seen, the speed of sound is faster in denser and more elastic media, such as steel and diamond, and slower in less dense media, such as air and light gases. Furthermore, temperature also plays a significant role in the speed of sound, as evidenced by the examples of oxygen and hydrogen at different temperatures.
Applications in scientific disciplines
The speed of sound is a magnitude of great relevance in numerous fields of science and technology.
Below are some of the most notable applications:
Acoustics and music
In the field of music and acoustics, the speed of sound is essential to understanding how sounds are produced and perceived. Musicians and sound technicians must consider the speed of sound when designing musical instruments and sound systems in large spaces to achieve faithful reproduction of desired frequencies and tonalities.
Medicine
Medical ultrasound uses the speed of sound to determine the depth and distance of tissues within the human body.
By emitting sound waves and measuring the time they take to return after bouncing off tissues, ultrasound machines can generate precise images of internal organs and structures.
Geophysics
The speed of sound is a fundamental tool in geophysical exploration.
In seismic prospecting, for example, sound waves are generated on the Earth's surface and the arrival times of these waves through different types of rocks and underground strata are recorded. This allows geologists and geophysicists to study the composition and structure of the subsurface.
civil Engineering
In civil engineering, it is crucial for the inspection of structures and the detection of defects. Ultrasound testing, which uses high-frequency sound waves, allows potential problems in construction materials, such as concrete and steel, to be identified without the need to destroy the structures.
Aviation and astronautics
In aviation and astronautics, the speed at which an object travels relative to the speed of sound is called the "Mach number."
Exceeding the speed of sound gives rise to the phenomenon known as a "sonic boom" or "sonic bang", which can have significant effects on nearby aircraft and structures.
Meteorology
In meteorology, the speed of sound is used to calculate the altitude of the layers of the Earth's atmosphere.
Radiosondes, which involve launching weather balloons equipped with sensors, measure temperature, humidity and pressure at different altitudes and use the speed of sound to determine air density.