[GreenKeys] Re: teletype machine noise levels

[gil smith]

Hi Allen:

I do have a 28-ASR and a 28-KSR, but I can't make any sound level tests on 
them as they are not in a position to be operated at the moment.  I have a 
28-TD somewhere as well, but it is a pretty quiet machine.

However, I happen to be printing some stuff out on a Model 15 today, so I 
took a few measurements with a sound level meter.

This twelve-year-old Radio Shack Sound Level Meter (model 33-2050) has seen 
little use, and I do not know whether it is accurate in any way.  According 
to the manual, the dB readings are "referenced to 0.00002 microbar" 
(whatever a bar is), with an accuracy of +/- 2 dB.  Then they say that "0 
dB = 0.0002 microbar," a factor of ten different from the previous 
paragraph.  So considering the source (radio-shlock), which I consider to 
make junk stuff anyway, and the contradictions in the cheesy little manual, 
I offer the following measurements for your amusement only.

The measurements were made in an office room, about 9' x 15', with wood 
floors, sheetrock walls/ceiling, desk, chair, some boxes -- not 
particularly sound-damping, but not completely reflecting.

I made the tests with the meter in A-weighting mode (primarily measures 
500-Hz to 10-KHz).  In the C-weighting mode (32-Hz to 10-KHz), the readings 
seemed one or two dB lower -- this seems wrong at first, since it is 
measuring a wider bandwidth.  But looking at the response graph in the 
manual, I see that freqs above 1KHz are measured a few dB down from the 
A-weighting.  This likely indicates the noise is primarily in the 1KHz to 
10 KHz range, though I did not dig out my spectrum analyzer to confirm 
this.  Anyway, A-weighting it is.

The meter was in the SLOW response mode.  In the FAST response mode, the 
meter needle just fluctuated within a dB of the slow reading.

Model 15 printing continuous text, with cover on, cover doors closed:
at 1 foot:   78 dB
at 5 feet:    72 dB
at 10 feet:   70 dB

Model 15 printing continuous text, with cover on, cover doors open:
at 1 foot:   83 dB
at 5 feet:    77 dB
at 10 feet:   75 dB

Model 15 printing continuous text, without cover:
at 1 foot:   90 dB
at 5 feet:    82 dB
at 10 feet:   80 dB

Model 15 not printing, motor on, without cover:
at 1 foot:   60 dB

Model 15 off (office noise only):
at 1 foot:   <50 dB

According to a chart in the rad-snack meter manual, typical A-weighted 
sound levels are:

20 dB:   quiet whisper
45 dB:   average house
65 dB:   conversation
75 dB:   average factory
80 dB:   loud orchestra
90 dB:   start of unsafe levels
130 dB:  pain threshold

for what it's worth,

gil smith


At 06:36 AM 9/21/2004, you wrote:
>Would it be possible for you to tell me what the decibel
>levels are for:
>
>Model 28 ASP (both with and without machine cover)
>Model 28 KSR (both with and without machine cover)
>Model 28 Tape Distributor (both with and without machine cover)
>
>Thank you for your time,
>
>____________________________________________________________________
>Allen G. Taylor, Vice President
>Management Information Systems
>Dura Builders - KB Home / Indianapolis Division
>5740 Decatur Blvd.
>Indianapolis, IN 46241
>
>(317) 821-8100 Ext.125 Voice
>(317) 821-1109 (FAX)
>
>PGP Key Signature: 24AE 2A2F A48B 7C73 AFBC  8369 1E72 D749 1B48 811B

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