People may want to think about this, taken from 2013 manual of motorcycle sport:
12.10 SOUND EMISSIONS - ALL DISCIPLINES
NOTE: From 1/7/2013 sound testing must be
carried out at all permitted events however it is
not mandatory to test all machines
12.10.1 Specifications
12.10.1.1 Sound emissions are set out in the
tables below:
30 meters (from side of track) ride by test
DISCIPLINE LIMIT dB(A)
Road Racing 95
Historic Road Racing 95
Classic MX & Dirt Track 95
Speedway (including Quads) 95
Dirt Track & Track (incl. Quads) 95
Record Attempts No limit
12.10.2 Use of sound level meters
12.10.2.1 Sound testing apparatus must:
a) Comply with international standard
IEC 651, Type 1 or Type 2.
b) Include a compatible calibrator, which
must be used immediately before
testing begins and always just prior to
a re-test if a disciplinary sanction may
be imposed.
12.10.2.2 Sound testing apparatus must be set to:
a) ‘Fast response’
b) ‘A’ weighted,
c) Select range High 80~130 dB,
e) Activate the function MAX MIN -
set on MAX,
12.10.2.3 ‘30 Meter ride by’ test
a) The sound levels will be measured
with the sound meter/microphone
fixed on a tripod, in the horizontal
position, 30 meters from the edge
of the track at a high speed point.
Cheers
Kim