User Guide

Plantronics Acoustic Safety White Paper

Draft #4

Plantronics Acoustic Safety

White Paper

INTERPRETING NOISE REGULATIONS INTO HEADSET LIMITS

The human ear ampliﬁes certain sounds more than others, making us more sensitive to hearing

the human voice. So, for a particular sound, a measurement in the “open ﬁeld” is very different

than a measurement inside of a human ear, at DRP. The difference is called Head Related Transfer

Function, or HRTF

. To compare an acoustic measurement on HATS, at DRP, to an “open ﬁeld”

regulatory acoustic safety requirement, the measurement result has to be translated to the

“open ﬁeld” equivalent by correcting with the HRTF.

However, for simplicity and convenience, telecom industry standards have historically speciﬁed a

long duration disturbance acoustic limit (similar to the continuous noise in OSHA) such as ITU-T

P.360, UL 60950-1 and ETSI EG 202 518. The requirement is 118 dBA

at about the opening to

the ear canal, called the Ear Reference Point, or ERP.

Acoustic startle is another sensitive and important concern for headset user, especially for contact

centers agents. Startle signals may not be high enough to cause hearing damages, yet they startle

users. They are annoying, stressful and certainly reduce headset listening comfort. Australian

Communications Industry Forum (ACIF) published a recommendation guide, G616, intended

to reduce acoustic startle incidence from headset. It requires headset receive output to be

<102 dBSPL at DRP. All Plantronics products with SoundGurad Digital comply with G616, see

the Plantronics product sheet on page 14 and 15 for detail.

WHO (World Health Organization) estimates that 1.1 billion young people worldwide could be at

risk of hearing loss due to unsafe listening practice. Regularly listening to music at high volume

and for long duration poses a serious threat to one’s hearing. IEC 62368-1 and EN 50332 specify

acoustic safety requirements for personal music player (PMP). The requirements are in two parts:

the player, e.g. mobile phones, and the listening device, e.g. multimedia headsets. The require-

ments limit the maximum electrical output from players and limit the maximum acoustic output

from listening devices with the maximum signal from players. There are two levels of maximum

output requirements from analog player, the level for an ordinary user is 27 mV, and the level for

instructed user is 150 mV. There is only one maximum acoustic output requirement from listening

device, it is ≤100 dBA with 150 mV input for analog or -10 dBFS input for digital. The test signal

is the “program simulation noise” speciﬁed by EN 60268-1. All Plantronics multimedia products

comply with PMP acoustic safety requirement, see the Plantronics product sheet on page 14 and

15 for detail.

THE BOTTOM LINE

A complex mix of HRTF, ERP and DRP based measurements explains the difference in the maximum

“open ﬁeld” noise levels noted in the US and EU regulations, and the lower maximum volumes

incorporated into the Plantronics acoustic protection technologies described in Section III.

For more information on HRTF, refer to ITU-T P.57, “Artiﬁcial ears”, ITU-T P.58 and IEEE Std 1652, “Free ﬁeld acoustic

reference to telephony measurements”.

There are some old European standards demand to meet 118 dBSPL without A-weighting.