The response factor represents a multiple of the level of vibration that is barely perceivable to a human. A response factor of 1 indicates a vibration that is just perceivable, a response factor of 2 represents twice that, and so on. The baseline curve that represents R=1 that is used in RAM Concept is from BS 6472 and is consistent with the ISO standard 2631-2. The curve is reproduced below. Like the velocity and acceleration plots, the response factor contour plots represent enveloped results of all the different analyses at each node. As such, the response factor contours are often used for evaluation of performance criteria. The following table lists some common response factor limits mentioned in BS 6472 and ISO 2631-2 for some different environments.