Click here to purchase the entire book in PDF format. Dynamic Range The dynamic range of your hearing is determined by two limits called the threshold of hearing and the threshold of pain. The threshold of hearing is the quietest sound that you are able to hear, specified at 1 kHz. This value is 20 $\mu$Pa or $20 * 10^{-6}$ Pascals. Just to give you an idea of how quiet this is, the sound of blood rushing in your head is louder to you than this. Also, at 20 $\mu$Pa of sound pressure level, the hair cells inside your inner ear are moving back and forth with a total peak-to-peak displacement that is much less than the diameter of a hydrogen atom . Note that the reference for calculating sound pressure level in dBspl is 20 $\mu$Pa, therefore, a 1 kHz sine tone at the threshold of hearing has a level of 0 dBspl. One important thing to remember is that the threshold of hearing is not the same sound pressure level at all frequencies, but we'll talk about this later. The threshold of pain is a sound pressure level that is so loud that it causes you to be in pain. This level is somewhere around 200 Pa, depending on which book you read, how masochistic you are and how often you go clubbing. This means that the threshold of pain is around 140 dBspl. This is very loud. In fact, if you had a powerful enough loudspeaker that could go just 20 dB higher than this - the sound would be loud enough that the air compression alone would generate enough heat to catch your hair on fire . So, based on these two numbers, we can calculate that the human hearing system has a total dynamic range (the difference between the maximum - the threshold of pain - and the minimum -the threshold of hearing) of about 140 dB.