Deutsche Version

Calculation

• Speed of sound c in air and the important temperature •

At 0 °C is ρ₀ = 1.293 kg/m³, Z₀ = 428 N·s/m³, and c₀ = 331 m/s
At 20 °C is ρ₂₀ = 1.204 kg/m³, Z₂₀ = 413 N·s/m³, and c₂₀ = 343 m/s
At 25 °C is ρ₂₀ = 1.184 kg/m³, Z₂₅ = 410 N·s/m³, and c₂₅ = 346 m/s
Air density or density of air = ρ, air impedance = Z, speed of sound = c

That means, the fraction p / ρ is always constant, even at "sea level". Forget the airpressure.

Generally we take with sufficient accuracy the formula for the speed of sound
in air in m/s vs. temperature (theta) in °C:

That gives e.g. at = 20 °C a speed of sound c = 331 + 0,6 · 20 = 343 m/s.

1 °C changing of temperature means 60 cm/s changing of speeed of sound.

With the following formula you can calculate more exactly the speed of sound.

Speed of sound in m/s; temperature in °C

The speed of sound c depends on the temperature of air and not on the air pressure!
The humidity of air has some negligible effect on the speed of sound. The air pressure
and the density of air (air density) are proportional to each other at the same temperature.
It applies always p / ρ = constant. rho is the density ρ and p is the sound pressure. The speed
of sound is alike on a mountain top as well as at sea level with the same air temperature.

Look for the answer of the question: "What is the speed of sound?"

Speed of sound - temperature matters, not air pressure

Density of air (air density) ρ = air pressure p / (gas constant R × temperature in Kelvin)
ρ = p / R × T (kg/m³)

The individual gas constant for dry air is R = 287,05 J/kg · K
Joule J = Newton · Meter = N m and T in Kelvin = °C + 273.15
Atmospheric pressure p₀ = 101325 Pa = 1013.25 mbar = 1013.25 hPa and R = 287.05J/kg · K
T₀ = 273.15 K at 0°C
ρ₀ = 101325 / (287.05 × 273.15) = 1.2923 kg/m³
T₂₀ = 293.15 K at 20°C
ρ₂₀ = 101325 / (287.05 × 293.15) = 1.2041 kg/m³

The speed of sound c is is not the sound velocity v.
The sound velocity is the particle velocity.

Table (chart): The impact of temperature
Speed of sound, density of air, acoustic impedance vs. temperature

Calculation of the speed of sound in humid air and the air pressure
Calculation of the wavelength of a wave in air when frequency and temperature is known

In gases, the higher the velocity of sound, the higher the pitch will be, when you sing.

In conventional use and in scientific literature sound velocity is the same as speed of sound or acoustic velocity.
Sound velocity c should not be confused with sound particle velocity v, which is the velocity of the individual particles.

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