<P> Note that in this example we have assumed that temperature is low enough that heat capacities are not influenced by molecular vibration (see heat capacity). However, vibrational modes simply cause gammas which decrease toward 1, since vibration modes in a polyatomic gas gives the gas additional ways to store heat which do not affect temperature, and thus do not affect molecular velocity and sound velocity . Thus, the effect of higher temperatures and vibrational heat capacity acts to increase the difference between the speed of sound in monatomic vs. polyatomic molecules, with the speed remaining greater in monatomics . </P> <P> By far the most important factor influencing the speed of sound in air is temperature . The speed is proportional to the square root of the absolute temperature, giving an increase of about 0.6 m / s per degree Celsius . For this reason, the pitch of a musical wind instrument increases as its temperature increases . </P> <P> The speed of sound is raised by humidity but decreased by carbon dioxide . The difference between 0% and 100% humidity is about 1.5 m / s at standard pressure and temperature, but the size of the humidity effect increases dramatically with temperature . The carbon dioxide content of air is not fixed, due to both carbon pollution and human breath (e.g., in the air blown through wind instruments). </P> <P> The dependence on frequency and pressure are normally insignificant in practical applications . In dry air, the speed of sound increases by about 0.1 m / s as the frequency rises from 10 Hz to 100 Hz . For audible frequencies above 100 Hz it is relatively constant . Standard values of the speed of sound are quoted in the limit of low frequencies, where the wavelength is large compared to the mean free path . </P>

Which of the following factors affect the speed of a sound wave