Elevation Speed Sound Air

Reference data and engineering information about elevation speed sound air for acoustics applications.

elevationspeedsoundair

Overview

Engineering reference data for Elevation Speed Sound Air in acoustics.

Key Formulas

Speed of Sound

$c = \sqrt{\gamma R T}$

Speed of sound in an ideal gas.

Wavelength

$\lambda = c / f$

Wavelength = speed / frequency.

Symbol	Description	Unit
$c$	Speed of sound	m/s
$L$	Sound level	dB
$\lambda$	Wavelength	m
$f$	Frequency	Hz

Speed of sound in dry air versus altitude based on the International Standard Atmosphere (ISA) model.
Elevation (m)	Elevation (ft)	Temperature (°C)	Temperature (°F)	Pressure (kPa)	Pressure (psi)	Speed of Sound (m/s)	Speed of Sound (ft/s)
-1000	-3281	21.5	70.7	113.9	16.52	344.1	1129
-500	-1640	18.3	64.9	107.49	15.59	342.2	1122
0	0	15	59	101.35	14.7	340.3	1116
250	820	13.4	56.1	98.32	14.26	339.3	1113
500	1640	11.8	53.2	95.49	13.85	338.4	1110
750	2461	10.1	50.2	92.67	13.44	337.4	1107
1000	3281	8.5	47.3	89.84	13.03	336.4	1103
1250	4101	6.9	44.4	87.15	12.64	335.5	1100
1500	4921	5.3	41.5	84.53	12.26	334.5	1097
1750	5741	3.6	38.5	81.98	11.89	333.5	1094
2000	6562	2	35.6	79.5	11.53	332.5	1091
2500	8202	-1.2	29.8	74.67	10.83	330.6	1084
3000	9843	-4.5	23.9	70.12	10.17	328.6	1078
3500	11483	-7.7	18.1	65.78	9.54	326.6	1071
4000	13123	-11	12.2	61.64	8.94	324.6	1065
4500	14764	-14.2	6.4	57.78	8.38	322.6	1058
5000	16404	-17.5	0.5	54.05	7.84	320.5	1051
5500	18045	-20.7	-5.3	50.54	7.33	318.5	1045
6000	19685	-23.9	-11.1	47.23	6.85	316.5	1038
6500	21325	-27.2	-17	44.06	6.39	314.4	1031
7000	22966	-30.4	-22.8	41.09	5.96	312.3	1024
7500	24606	-33.7	-28.6	38.33	5.56	310.2	1017
8000	26247	-36.9	-34.5	35.65	5.17	308.1	1011
8500	27887	-40.2	-40.3	33.16	4.81	305.9	1003
9000	29528	-43.4	-46.2	30.82	4.47	303.8	996
9500	31168	-46.7	-52	28.61	4.15	301.7	990
10000	32808	-49.9	-57.8	26.48	3.84	299.5	982
11000	36089	-56.4	-69.5	22.68	3.29	295.2	968
12000	39370	-56.4	-69.5	19.37	2.81	295.1	968
13000	42651	-56.4	-69.5	16.62	2.41	295.1	968
14000	45932	-56.4	-69.5	14.2	2.06	295.1	968
15000	49213	-56.4	-69.5	12	1.74	295.1	968
16000	52493	-56.4	-69.5	10.34	1.5	295.1	968
17000	55774	-56.4	-69.5	8.83	1.28	295.1	968
18000	59055	-56.4	-69.5	7.58	1.1	295.1	968
19000	62336	-56.4	-69.5	6.48	0.94	295.1	968
20000	65617	-56.4	-69.5	5.52	0.8	295.1	968
25000	82021	-51.6	-60.9	2.55	0.37	298.4	979
30000	98425	-46.7	-52	1.17	0.17	301.7	990
32000	104987	-44.7	-48.5	0.9	0.13	303	994

While the table provides direct values, the speed of sound in dry air, $c$ , is primarily a function of temperature, $T$ . The most common approximate formula for dry air at low to moderate altitudes is:

$c \approx 331.3 \sqrt{1 + \frac{T}{273.15}}$

where:

$c$ is the speed of sound in meters per second (m/s).
$T$ is the air temperature in degrees Celsius (°C).

For higher accuracy, especially in scientific contexts, a more precise formula is used:

$c = \sqrt{\gamma R T}$

where:

$\gamma$ is the adiabatic index (ratio of specific heats, ~1.4 for dry air),
$R$ is the specific gas constant for dry air (~287.05 J/(kg·K)),
$T$ is the absolute temperature in Kelvin (K).

A key observation from the data is that above the tropopause (approximately 11,000 meters), the temperature stabilizes in the International Standard Atmosphere model. Consequently, the speed of sound becomes nearly constant (~295 m/s) across a range of altitudes, despite the continued drop in air pressure.