RE: Ear protection

[Erik Sundberg <ESundberg () nitelusa com>]

These block out the loud noise but allow you to still talk.

Surefire Sonic Defender EP3, Ep4, EP5, EP7

They all are great!

http://www.amazon.com/Surefire-Sonic-Defender-Plugs-1-Pair/dp/B007FKY8SI/ref=sr_1_8?ie=UTF8&qid=1443029640&sr=8-8&keywords=surefire+ep3+ep4



-----Original Message-----
From: NANOG [mailto:nanog-bounces () nanog org] On Behalf Of Lamar Owen
Sent: Wednesday, September 23, 2015 11:13 AM
To: NANOG <nanog () nanog org>
Subject: Re: Ear protection

On 09/23/2015 10:09 AM, Keith Stokes wrote:
> Since I’m in our colo facility this morning, I decided to put some numbers on it in my little isolated corner with 
> lots of blowers running.
>
> According to my iPhone SPL meter, average SPL is 81 - 82 dB with peaks 88 - 89 dB.
With SPL that close to the recommended maximum, the accuracy of the SPL measurement is rather critical.  I would not 
trust my smartphone's mic to have sufficient accuracy to protect my hearing unless it is calibrated to a known source 
SPL using pink noise of a particular weight.  The calibration SLM should be a 'real' SLM, such as a Bruel & Kjaer Type 
2250 or similar with proper transducers.  (Yes, I know, a B&K
2250 will set you back nearly $4K, but, just what is your hearing worth?  A pair of hearing aids will set you (or your 
insurance company at least) back $4K too....).  I used a vintage B&K transducer with a custom-built SLM-rated spec-an 
years ago at a local manufacturer's sound testing lab; the manufacturer makes ballasts and luminaires for HID lighting, 
and measuring ballast noise is a big deal.  But reasonably accurate SLM's are available for less than $500 (some are 
available for less than $100, but you get what you pay for....).

The particular whine of high-speed fans is a known risky noise source, particularly white noise, due to the high 
frequency content (140dB SPL at 45Hz is not as harmful as 140dB at 3kHz or 15kHz due to the outer ears' acting as 
waveguide-beyond-cutoff attenuators (and cavity resonators, too, for that matter).  Spinning drives are no better, 
particularly 15k  RPM drives.

If it's at all uncomfortable, wear the earplugs.  You're already having to shout to be heard anyway.


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