(15C) Speed of Sound in Air
04-10-2024, 02:58 AM
Post: #1
 Eddie W. Shore Senior Member Posts: 1,585 Joined: Dec 2013
(15C) Speed of Sound in Air
Formula used:

The speed of sound in air can be approximated by:
c ≈ √( γ * R * T / M)

where:

R = molar gas constant = 8.314 4625 618 153 J/(K * mol)
R = 8.314 4625 618 153 (kg * m^2)/(s^2 * K * mol)

M = molar mass of air = 0.02897 kg/mol

γ = adiabatic index of air = 1.4

C ≈ 20.04503702 * √T ≈ 331.2893427 * √((°C + 273.15) / 273.15)

Instructions:

To calculate the speed of sound when the temperature is in Fahrenheit (°F), press [ f ] { A } or [ GSB ] { A } [ R/S ].

To calculate the speed of sound when the temperature is in Celsius (°C), press [ f ] { B } or [ GSB ] { B } [ R/S ].

To calculate the speed of sound when the temperature is in Kevin (K), press [ f ] { C } or [ GSB ] { C } [ R/S ].

Code:
Code:
 Step ; Key Code ; Key 001 ; 42, 21, 11 ; LBL A 002 ; 3 ; 3 003 ; 2 ; 2 004 ; 30 ; - 005 ; 5 ; 5 006 ; 20 ; × 007 ; 9 ; 9 008 ; 10 ; ÷ 009 ; 42, 22, 12 ; LBL B 010 ; 2 ; 2 011 ; 7 ; 7 012 ; 3 ; 3 013 ; 48 ; . 014 ; 1 ; 1 015 ; 5 ; 5 016 ; 40 ; + 017 ; 42, 22, 13 ; LBL C 018 ; 11 ; √ 019 ; 2 ; 2 020 ; 0 ; 0 021 ; 48 ; . 022 ; 0 ; 0 023 ; 4 ; 4 024 ; 5 ; 5 025 ; 0 ; 0 026 ; 3 ; 3 027 ; 7 ; 7 028 ; 0 ; 0 029 ; 2 ; 2 030 ; 20 ; × 031 ; 36 ; ENTER 032 ; 36 ; ENTER 033 ; 2 ; 2 034 ; 48 ; . 035 ; 2 ; 2 036 ; 3 ; 3 037 ; 6 ; 6 038 ; 9 ; 9 039 ; 3 ; 3 040 ; 6 ; 6 041 ; 20 ; × 042 ; 34 ; X<>Y 043 ; 43, 32 ; RTN

Examples:

68 °F: 68 [ f ] { A } -> 343.20358 m/s, 767.72445 mph
35 °C: 35 [ f ] { B } -> 351.87462 m/s, 787.83024 mph
280 K: 280 [ f ] { C } -> 335.41762 m/s, 750.30776 mph

Source

“Speed of Sound” Wikipedia. Last Edited March 27, 2024. https://en.wikipedia.org/wiki/Speed_of_sound Retrieved April 7, 2024
04-11-2024, 01:26 PM (This post was last modified: 04-12-2024 11:19 AM by Gil.)
Post: #2
 Gil Senior Member Posts: 613 Joined: Oct 2019
RE: (15C) Speed of Sound in Air
With the above formulae and data, and applying 1st order Taylor development (to get rid of the square root), you get this easy to remember formulae, and very simple to apply without a calculator:

c[m/s] about 331.3 + 0.61×T[in Celsius] or