The response factor is a multiplier on the level of vibration at the threshold of human perception. Thus, a response factor of 1 would represent a level of vibration that is just at the threshold of human perception, and a response factor of 2 would represent twice the perceivable level.. People are more sensitive to vibration at some frequencies than at others. The base curves for human perceivability are taken from BS 6472. Since vibrations can contain a range of frequencies, the response factor in RAM Concept is calculated individually for each harmonic excitation frequency by taking a baseline acceleration (a_RMS = 1) from the curve for that frequency, then combined using square root of sum of squares (SRSS). For resonant response, the response factor is always calculated using accelerations.