Hi
the Tensor Tympani muscle is in the middle ear
not the inner ear. It has a latency of about 40 Msec. The stapidius muscle which is also in the middle ear is much faster and has a latency of about 10 msec and a threshold of about 85dBSPL. The stapedius muscle will activate at 85 and saturate at about 120 dBSPL and at frequencies below 1000Hz.