Temperature dependence of physical entities - speed of sound density of air acoustic impedance dependency - sengpielaudioChecker
 
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Temperature Dependence of Physical Entities
Speed of sound, Density of air and Air impedance

Temperature
of air vartheta in °C		 Speed of sound
c in m/s 		Time per 1 m
Δ t in ms/m		 Density of air
ρ in kg/m3		 Impedance
of air Z in N·s/m3
+35 351.96 2.840 1.1455 403.2
+30 349.08 2.864 1.1644 406.5
+25 346.18 2.888 1.1839 409.4
+20 343.26 2.912 1.2041 413.3
+15 340.31 2.937 1.2250 416.9
+10 337.33 2.963 1.2466 420.5
 +5 334.33 2.990 1.2690 424.3
 ±0 331.30 3.017 1.2920 428.0
 −5 328.24 3.044 1.3163 432.1
−10 325.16 3.073 1.3413 436.1
−15 322.04 3.103 1.3673 440.3
−20 318.89 3.134 1.3943 444.6
−25 315.72 3.165 1.4224 449.1

Vartheta = Temperature, c = Speed of sound, ρ = Density of air, Z = Acoustic Impedance of air

The speed of sound in air is determined by the air itself and is not
dependent upon the amplitude, frequency, or wavelength of the sound.
For an ideal gas the speed of sound depends only on the temperature and
is independent of gas pressure. This dependence also applies to air, in
good approximation and can be regarded as an ideal gas.

Aha! Notice: The speed of sound changes clearly with temperature,
              a little bit with humidity − but not with air pressure (atmospheric pressure).
              The words "sound pressure at sea level" are incorrect and misleading.
              The temperature indication, however, is absolutely necessary.

Properties of sound in air

Enter simply the value to the left or the right side.
The calculator works in both directions of the ↔ sign.
 
Temperature ϑ  (theta):
°C		  ↔  Speed of sound v:
m/s
Frequency f:
Hz		  ↔  Wavelength λ:
m
 

The effect of temperature

The air density is: ρ = p / (R · T) in kg/m3, Air pressure = p, Gas constant = R,
Temperature in Kelvin = T

The individual gas constant R
for dry air is:

R = 287,058 J / kg · K

with energie Joule (J) = Newton · Meter = N m; T in Kelvin = Temperature in °C + 273.15.

Atmospheric pressure p0 = 101325 Pa = 1013.25 mbar = 1013.25 hPa und R = 287.058 J/kg · K.

With the temperature of T0 = 273.15 K (0 °C) the density of air is:

ρ0 = 101325 / (287.058 · 273.15) = 1.2922 kg/m3.

For T25 = 298,15 K (25°C) (Normal conditions) the density of air is:

ρ25 = 101325 / (287,058 · 298,15) = 1.184 kg/m3.

Furthermore it is customary T20 = 293.15 K ⇔ 20°C and the density of air is ρ = 1.204 kg/m3.

As you see, this sizes are strongly temperature dependent.

The speed of sound in air is:
Schallgeschw
Vartheta (theta) is the temperature in degrees Celsius.

Z0 = ρ0 · c      Z0 is the specific acoustic impedance of air and c is the speed of sound.

Google is not correct (look at the following link)
http://www.google.com/search?q=speed+of+sound+at+sea+level
Here is the answer of Google: "Speed of sound at sea level = 340.29 m/s".
This is not a good answer, because they forgot to tell us the important temperature,
and the given atmospheric pressure "at sea level" makes really no sense.

Reason: The static air pressure p_ and density ρ of the air at the same temperature
are proportional to each other. The ratio p / ρ is always constant, on a high
mountain or even at sea level. Forget the atmospheric pressure, but make
sure the important temperature.

Weiter

Adiabatic index or ratio of specific heats κ (kappa) = cp / cv. Generally we take
with sufficient accuracy the formula (equation) for the speed of sound in air
in m/s vs. temperature Vartheta (theta) in degrees Celsius (centigrade):

 
 Schall in m/s. 
 

That gives e.g. at Vartheta = 20°C a speed of sound c = 331 + 0.6 × 20 = 343 m/s.

 
 1 °C change of temperature is equal to 
 60 cm/s change of speed of sound.
 

Pitch change by temperature change (variation)
Calculation of the Speed of Sound in Air and the important Temperature
Speed of sound - temperature matters, not air pressure
Calculation: speed of sound in humid air

 
Note: The radiated sound power (sound intensity) is the cause -
and the sound pressure is the effect.
The effect is of particular interest to the sound engineer.
The effect of temperature and sound pressure.
 

 
Acousticians and sound protectors (noise fighters) need the
sound intensity (acoustic intensity). As a sound designer you
don't need that. Look out more for the sound pressure that
makes effects to your ears and to the microphones.
 

Sound pressure and Sound power – Effect and Cause

Converter: Fahrenheit to Celsius and Celsius to Fahrenheit

To use the calculator, simply enter a value.
Calculator works in both directions of the ↔ sign.

 
Temperature in Fahrenheit:
 °F		  ↔  Temperature in Celsius:
 °C
 °F = °C × 1,8 − 32    °C = (°F − 32) / 1,8
 

Formulas to convert from and to Celsius (Centigrade)
 
  from Celsius to Celsius
Fahrenheit [°F] = [°C] × 9/5 + 32 [°C] = ([°F] − 32) × 5/9
Kelvin [K] = [°C] + 273.15 [°C] = [K] − 273.15
Rankine [°R] = ([°C] + 273.15) × 9/5 [°C] = ([°R] − 491.67) × 5/9
Delisle [°De] = (100 − [°C]) × 3/2 [°C] = 100 − [°De] × 2/3
Newton [°N] = [°C] × 33/100 [°C] = [°N] × 100/33
Réaumur [°Ré] = [°C] × 4/5 [°C] = [°Ré] × 5/4
Rømer [°Rø] = [°C] × 21/40 + 7.5 [°C] = ([°Rø] − 7.5) × 40/21

Formulas to convert from and to Fahrenheit
 
  from Fahrenheit to Fahrenheit
Celsius [°C] = ([°F] − 32) × 5/9 [°F] = [°C] × 9/5 + 32
Kelvin [K] = ([°F] + 459.67) × 5/9 [°F] = [K] × 9/5 − 459.67
Rankine [°R] = [°F] + 459.67 [°F] = [°R] − 459.67
Delisle [°De] = (212 − [°F]) × 5/6 [°F] = 212 − [°De] × 6/5
Newton [°N] = ([°F] − 32) × 11/60 [°F] = [°N] × 60/11 + 32
Réaumur [°Ré] = ([°F] − 32) × 4/9 [°F] = [°Ré] × 9/4 + 32
Rømer [°Rø] = ([°F] − 32) × 7/24 + 7.5 [°F] = ([°Rø] − 7.5) × 24/7 + 32
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