For bone conduction ABR, the transducer output is quoted re 1 microvolt
based on the fact that for an SLM 1 volt is equivalent to 120 dB and
therefore 1 microvolt is equivalent to 0 dB. When calibrating using an
artificial mastoid a correction of the order of 20 dB in respect of SLM
measurement to account for the sensitivity of the transducer in the
artificial mastoid is necessary. 0 dBnHL corresponds to about 35 dB force
(re 1 microvolt).
In the USA, the imperial system means that the reference is 1 dyne, which
is 1/100 000 Newton, whilst in the above 1 microvolt represents 1
micronewton of force. Could someone in the USA then enlighten me as to
how the US literature historically refers to 0 dBnHL as 35 dB force (re 1
dyne) which would seem 20 dB too high.