HP Color LaserJet 4650 Printer series - Manual (Page 257)

Acoustic emissions
Sound Power Level Declared Per ISO 9296
Active (22 ppm letter)
Idle
L
WAd
=6.5 Bels (A) [65 dB (A)]
L
WAd
=5.0 Bels (A) [50 dB (A)]
SPL - Bystander Position Declared Per ISO 9296
Active (22 ppm letter)
Idle
L
pAm
=51 dB (A)
L
pAm
=34 dB (A)
Note Values are subject to change. See http://www.hp.com/support/lj4650 for current information.
ENWW Acoustic emissions 243