System Acoustic Calibration - Cambridge Sound Management Qt Emitters Installation And Operation Manual

SYST E M SE T- UP AND CALIBR ATIO N

System acoustic calibration

Setting the masking volumes can be approached in one of three ways:
Best:
The Qt system has a companion iPad app that takes acoustic measurements and relays the results to
the control module via Bluetooth to set the appropriate masking sound level. See Qt CRE Configuration
App Manual.
Good:
If a sound level meter is available it is recommended that initially the control module's masking volume
be adjusted up or down to achieve the values below. If the meter has a speed setting, set it to "Slow."
Weighting should be set to "A."Peak readings should be ignored, the appropriate value is the RMS or
"eyeball" average level.
37-40 dB in the 2 kHz octave or 45-48 dBA, measured 3-4 ft. (0.9 m) above floor level and averaged
spatially.
Otherwise:
If a calibrated sound level meter is not available, the recommended levels are likely to be achieved in
most office environments by setting the control module's masking volumes as follows:
13-16, for 8 ft. (2.4 m) ceilings
15-18, for 10 ft. (3 m) ceilings
17-20, for 12 ft. (3.6 m) ceilings
Masking volumes must be set sufficiently high to achieve Confidential speech privacy but not so high
that the masking sound becomes obtrusive. Settings within the above ranges typically accommodate
both objectives. As a general rule, use the high end of the range but base final settings on site
conditions and customer preferences.
Special installation cases
When to leave sound masking on continuously
1.
There are cases where leaving the masking on continuously will minimize awareness of its operation.
If the masking level in the emitter-covered area needed to adequately mask speech from the
conference room into adjacent space is determined to be below 40 dBA we suggest leaving it on
24/7. This normally will be feasible only with very good sound isolating construction between the
conference room and adjoining spaces. Likewise, if a separate office-wide masking system is already
in place and the QtCRE is intended merely to provide an extra margin of confidentiality around the
sensitive space it can normally be left on continuously.
Adjacent conference rooms
2.
If adjacent conference rooms are separated solely by sufficiently poor sound isolating construction,
Qt Conference Room Edition Installation and Operations Guide page 29