(15C) Speed of Sound in Air - Printable Version +- HP Forums (https://www.hpmuseum.org/forum) +-- Forum: HP Software Libraries (/forum-10.html) +--- Forum: General Software Library (/forum-13.html) +--- Thread: (15C) Speed of Sound in Air (/thread-21581.html) (15C) Speed of Sound in Air - Eddie W. Shore - 04-10-2024 02:58 AM 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 RE: (15C) Speed of Sound in Air - Gil - 04-11-2024 01:26 PM 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 c[m/s] about 331+ 0.6×T[in Celsius]. For Fahrenheit c[m/s] about 320.6+ 1/3×T[in Fahrenheit] or c[m/s] about 321+T/3[in Fahrenheit]. Gil