Radio Shack 33-2055A User manual

Owner’s Manual Please read before using this equipment.
Digital Sound Level
Meter

2
ˆ Contents
Features ............................................... 3
Installing the Battery ........................... 5
Making Measurements ........................ 7
Setting the Sound Range ............... 7
Setting the Weighting ..................... 8
Setting the Response ..................... 9
Making Normal Measurements .... 10
Making Maximum Measurements 12
Level Indications .......................... 12
Underrange Indication .......... 13
Overrange Indication ............ 14
Using Data Hold ........................... 15
Making an Integrated Average
Measurement ............................... 16
Making Maximum and Minimum
Measurements During an
Undetermined Time Period .......... 19
Checking Stereo System
Acoustics ...................................... 20
Calibrating the Meter .................... 20
Care .................................................... 21
Specifications .................................... 22
©2000 RadioShack Corporation. All Rights Reserved.
RadioShack and RadioShack.com are trademarks used
by RadioShack Corporation.

3
Features
ˆ Features
Your new RadioShack Digital Sound Lev-
el Meter precisely measures area noise
and other sound levels. The meter’s digital
design and special measuring features,
such as the bargraph and date hold, en-
sure pinpoint accuracy for checking an
acoustic environment. The meter is light-
weight and easy to operate.
Note: This meter should be used for
home/hobbyist use only. This meter
does not meet the requirements set
forth by the American National Stan-
dards Institute (ANSI), Standard S1.4.
Your meter also has these features:
3-Digit Liquid Crystal Display — makes
it easy to read sound measurements.
21- Dot Analog Bargraph — gives you a
visual representation of the measured
sound.
Mode/Condition Indicators — show you
the current mode and status of the meter.

4Features
Wide Sound-Measuring Abilities —
measures from 50 dB to 126 dB SPL with
seven ranges.
Average or Maximum Sound Level Dis-
play — continuously shows the average
or maximum sound level: per second with
digits, per 0.2 or 0.5 seconds with the bar-
graph.
Tripod Ready — lets you attach the
meter to a tripod (1/4-inch) for more accu-
rate sound measurements.
Date Hold — lets you
freeze
a measure-
ment on the display.
Integrated Averaging — measures the
integrated average, and holds the maxi-
mum and minimum sound levels for a pre-
set period.
Underrange and Overrange Indicators
— show you when the sound level reading
is under or over the selected range.
A and C Weighting — lets you select ei-
ther type of weighting to suit the purpose
of the measurement.
Selectable Bargraph Response — lets
you select a slow (0.5 second) or fast (0.2
second) bargraph response.

5
Installing the Battery
Peak Level Indication — shows you
when the meter registers the maximum
level measurement on the bargraph.
Reset Button — lets you clear the current
measurements from the meter’s memory
and begin a new measurement.
9-Volt Battery Operation — lets you
power the meter with a 9-volt battery.
Phono Output Jack — lets you connect
the meter to your stereo system or test
equipment.
Low-Battery Indicator — shows you
when the battery needs to be replaced.
ˆ Installingthe
Battery
The meter requires one 9-volt battery for
operation. For the best operation and
longest life, we recommend RadioShack
alkaline batteries. Follow these steps to
install the battery.

6Installing the Battery
1. Set RANGE to OFF.
2. Remove the bat-
tery compartment
cover by pressing
in both sides and lifting off the cover.
3. Install the battery as indicated by the
diagram marked in the compartment.
Place the battery over the red ribbon
to make it easy to remove the battery
later.
4. Replace the battery compartment
cover.
Notes:
• When you are not using the meter,
set
RANGE to OFF.
• If you will not use the meter for a
week or more, remove the battery.
• When the battery becomes low,
BATT appears on the display.

7
Making Measurements
Replace the battery with a fresh one
of the same type.
ˆ Making
Measurements
SETTING THE SOUND
RANGE
The meter can measure sound levels
within seven different ranges. Each range
covers 20 dB. The number of each range
represents the center of the range. For ex-
ample, if you set RANGE to 70, the meter
measures sound levels from 60 to 80 dB.

8Making Measurements
Set RANGE for the approximate sound lev-
el you want to measure. If you do not
know the sound level, start with the high-
est range setting (120) and gradually re-
duce the setting. When the measured
value is lower or higher than the set
range, an underrange or overrange indi-
cator appears. See “Level Indications” on
Page 12.
Notes:
• If you set RANGE to 120, the meter
measures sound levels from 110 dB
to 126 dB.
• If you change the range setting during
a measurement, you clear all the cur-
rent data and a normal continuous
measurement resumes.
SETTING THE WEIGHTING
WEIGHTING lets you set the meter’s
weighting characteristics, which deter-
mine the meter’s frequency response
curve. You can select
A-weighting
or
C-
weighting
.
A-weighting has A-curve frequency char-
acteristics. This setting causes the meter
to respond mainly to frequencies in the

9
Making Measurements
500-to-10,000 Hz range, which is the hu-
man ear’s most sensitive range. Select A-
weighting to determine an area’s noise-
level. Take measurements at several dif-
ferent points in the area.
C-weighting has C-curve (flat) frequency
characteristics. This setting causes the
meter to respond mainly to frequencies in
the 32 to 10,000 Hz range. Select C-
weighting to measure sound levels of mu-
sical material.
When you set RANGE to OFF, the meter
automatically selects C-weighting.
Press WEIGHTING to change the weight-
ing between A and C.
The display shows the current setting
(WEIGHTING A or WEIGHTING C).
Note: You can change the weighting set-
ting only during a continuous average or
maximum measurement.
SETTING THE RESPONSE
RESPONSE lets you set the interval at
which the meter revises the bargraph
sound level reading. There are two set-
tings –
fast
and
slow
. When you set

10 Making Measurements
RANGE to OFF, the meter automatically
sets the response for
fast
.
At the fast setting, the meter revises the
bargraph reading after about every 0.2
seconds. At the slow setting, the meter re-
vises the reading after about every 0.5
seconds.
Press RESPONSE to change the bar-
graph’s response between fast and slow.
The display shows the selected setting
(RESPONSE SLOW or RESPONSE
FAST).
Note: You can change the response set-
ting only during a continuous average or
maximum measurement.
MAKING NORMAL
MEASUREMENTS
Follow these steps to measure the aver-
age sound level.
1. Set RANGE for the desired sound
range. If you do not know the sound
level, start at the highest range set-
ting (120) and reduce the setting until
you get a reading. (See “Setting the

11
Making Measurements
Sound Range” on Page 7 and “Level
Indications” on Page 12.)
2. Set the weighting and response. (See
“Setting the Weighting” on Page 8
and “Setting the Response” on
Page 9.)
3. Face the sound source. Then hold
the meter to one side and point its
microphone at the sound source.
The meter begins to display the
con-
tinuous average
sound level. This is
the average sound level during a 1-
second sampling period, which the
meter updates once per second. The
bargraph shows the continuous aver-
age for either a 0.2-second or 0.5-
second period, depending on the
response setting.
When you complete a measurement, set
RANGE to OFF.

12 Making Measurements
MAKING MAXIMUM
MEASUREMENTS
To measure the continuous maximum
sound level, follow the steps in “Making
Normal Measurements” on Page 10 and
press MAX so MAX appears on the dis-
play.
The meter displays only the loudest mea-
sured sound level during the 1-second
sampling period. The bargraph shows the
maximum level of every 0.2 or 0.5 sec-
onds. The bargraph segment that corre-
sponds to the peak reading stays on the
display for 2 seconds or until the meter
measures a higher maximum level.
Press MAX again to cancel the continu-
ous maximum measurement and resume
a normal continuous average measure-
ment.
LEVEL INDICATIONS
The meter displays the sound level using
numbers and a bar graph. The numbers
show the sound level in dB within ±10 dB
of the selected range and the meter up-
dates the reading once per second.

13
Making Measurements
The bargraph’s center point represents
the center level of the selected range (60
dB, 70 dB, 80 dB, and so on).
The points to the left of the center indicate
measurements less than the center level
(down to –10 dB below the selected
range). The points to the right of the cen-
ter indicate measurements greater than
the center level (up to +10 dB above the
selected range).
The bargraph updates every 0.2 or 0.5
seconds, depending on the response set-
ting. (See “Setting the Response” on
Page 9.)
Underrange Indication
When the measured sound level is lower
than the lowest sound level of the select-
ed range, LO appears and the bargraph

14 Making Measurements
disappears. If this happens, select a lower
range.
Overrange Indication
When the measured sound level is higher
than the highest sound level of the select-
ed range (except for the 120 dB range),
the bargraph and digits that represent the
next higher range flash on the display.
For example, if the meter measures 91 dB
in the 80 dB range, 90 and the bargraph
flash.
If the meter measures more than 126 dB
in the 120 dB range, 126 and the bargaph
flash.

15
Making Measurements
If you get an overrange indication, change
the range setting until you get a reading in
the upper half of the range (0 to + 10 dB).
Notes:
• The underrange or overrange indica-
tion can also appear when you recall
a measurement using data hold and
the measurement is under or over the
selected range. See “Using Data
Hold.”
• The meter cannot measure sound
levels lower than 50 dB or higher than
126 dB.
USING DATA HOLD
The data-hold function lets you store the
current measurements in memory and
freeze
a measurements on the display.
The meter stores the continuous average,
the maximum, and the minimum sound
levels for the last 1 second.
To store the current measurements, press
DH during a continuous average or maxi-
mum measurement. The last average
measurement or last maximum measure-
ment (with MAX) appears on the display.

16 Making Measurements
Press MAX to freeze the current maximum
measurement if the last average mea-
surement (without MAX) is on the display.
Press MAX again to return to the average
measurement.
Press MIN to freeze the current minimum
measurement. MIN also appears on the
display. Press MIN again to return to the
average measurement.
Press RESET to return to a continuous av-
erage or maximum measurement.
Notes:
• You cannot change the response and
weighting settings during data hold.
• When you set RANGE to a different
range during data hold, you cancel
the function and return to a continu-
ous measurement.
MAKING AN INTEGRATED
AVERAGE MEASUREMENT
Follow these steps to monitor the sound
level and average the measurement over
a preset time period of 1 to 199 seconds.
The meter stores the average, the maxi-

17
Making Measurements
mum, and the minimum sound levels dur-
ing the set time period.
1. Press DH for about 2 seconds during
a continuous average or maximum
measurement.
1appears on the dis-
play.
2. Repeatedly press or hold down MAX
or MIN to set the desired measuring
period from 1 to 199 seconds.
3. Position the meter for the measure-
ment.
4. Press RESET to start the monitoring.
The meter measures the integrated aver-
age, maximum, and minimum sound lev-
els for the set time. The meter updates the
current integrated average display every
second and MIN and MAX flash until the
set time ends.
When the set time ends, DH appears, and
MIN and MAX continue to flash. The

18 Making Measurements
meter displays the total integrated aver-
age sound level.
Press MAX to display the maximum sound
level for the set time. Press MAX again to
return to the total integrated average
sound level.
Press MIN to display the minimum sound
level for the set time. Press MIN again to
return to the total integrated average
sound level.
Press RESET after you check the integrat-
ed average sound level and the maximum
or minimum sound level. The meter re-
sumes a continuous average measure-
ment.
Note: If you change the RANGE setting
during an integrated measurement, you
clear any stored data and a normal contin-
uous average measurement resumes.

19
Making Measurements
You must repeat the procedure for making
an integrated average measurement.
MAKING MAXIMUM AND
MINIMUM MEASUREMENTS
DURINGANUNDETERMINED
TIME PERIOD
You can check the maximum and mini-
mum sound level over any length of time.
To do so, press RESET during a continu-
ous average or maximum average mea-
surement.
At the end of the desired time period,
press
DH.
DH appears.
To display the maximum sound level dur-
ing the time period, press MAX if both MIN
and MAX flash on the display and the last
average sound level appears. Press MAX
again to return to the average sound level.
Note: If only MIN flashes on the display,
the meter is already showing the maxi-
mum sound level during the time period.
Press MIN to display the minimum sound
level during the time period. Press MIN
again to return to the last average sound
level.

20 Making Measurements
Press RESET after you check the maxi-
mum or minimum sound level. The meter
resumes a normal continuous average or
maximum measurement.
CHECKING STEREO
SYSTEM ACOUSTICS
To check the sound of a stereo system,
use a test recording that produces pure
tones, one at a time, at intervals that span
the entire audio spectrum.
Use C-weighting with either slow or fast
response.
Make a graph or table that shows the
sound level each tone generates. This
gives you a clear idea of the frequency re-
sponse of the total audio system – includ-
ing the room. To smooth out the
response, adjust the tone control, vary the
speaker placement, and use a frequency
equalizer.
CALIBRATING THE METER
The recessed calibration control (labeled
CAL on the meter’s left side) is intended
for service technicians only.