import math


def speed_of_sound(p, rho, gamma):
    """Calculate perfect gas speed of sound

    :param <float> p: Pressure (Pa)
    :param <float> rho: Density (kg/m^3)
    :param <float> gamma: Specific heat ratio

    :return <float> a (m/s)
    """

    return math.sqrt(gamma * p / rho)