USER GUIDE
ASM-2 — Seven-Range Sound Level Meter
INTRODUCTION
Congratulations on your purchase of the Nady ASM-2 sound level meter. You’ll find that it is an extremely versatile
device for measuring sound intensity in just about any acoustic environment-loud or soft; high-pitched, low-pitched,
or broad-band; intermittent or continuous. You can use it to measure noise levels in factories, schools, offices, and
airports, or to check acoustics of studios, auditoriums, and home theater installations.
Your meter features a large, easy-to-read indicator for taking quick measurements anywhere. Power is supplied by
a 9-volt alkaline or NiMH battery, so the meter is completely portable.
The meter’s other features include:
• Seven sound-level ranges—allow measurements from 50 - 126 dB (referenced to 0.0002µbar).
• A and C weightings—lets you check compliance with safety regulations as well as make acoustic analysis.
• Slow and fast response settings—let you check peak and average noise levels.
• Built-in battery condition indicator
• Phono-type output jack—for connection to home theater or test equipment.
• The Threaded insert—lets you attach the meter to a camera tripod for increased accuracy.
INSTALLING A BATTERY
The meter uses a 9-volt battery. For the longest life and best performance, we recommend an alkaline battery.
Open the battery compartment cover by pressing both sides at the lower striped portion and lifting the bottom. Insert
a battery into the compartment as indicated by the polarity markings (+ and -) marked inside.
To test the battery, set RANGE to BATT. If the meter shows a reading in the red BATT TEST region, the battery is
still good.
Notes:
• Leave RANGE in the OFF position when the meter is not in use to conserve battery power.
• Remove the battery if you are not going to use the meter for a week or more.
RANGE
The RANGE selector lets you select one of seven sound level ranges, each spanning 16 dB. The numbers on
RANGE refer to the center points of the seven ranges. The needle indicator shows the actual sound level as a
displacement from the center point. For example, if RANGE is set to 80 and the meter scale reads -3, the actual sound level is 77 as the value where RANGE
is set, the actual sound level is 80 dB (80+0).
OUTPUT
The phonotype OUTPUT jack lets you connect the meter to recording or other measurement equipment. For example, you might use an audio patch cord to
connect the meter to the AUX or high-level input of a recorder. Note that the meter response will not be flat, due to the A- and C-weighting networks.
Set Range so the maximum needle deflection is never greater than +4, to prevent the built-in amplifier from clipping. Use A-weighting for voice recordings, or
C-weighting for full-range musical material. The OUTPUT jack can also be connected to high-impedance headphones, or an oscilloscope, a frequency
analyzer, or other test equipment.
RESPONSE
The RESPONSE selector has two settings: FAST and SLOW. In the FAST position, the meter reacts quickly to changes in the sound level, showing you the
peak sound levels present in the enviroment. In the SLOW position, the meter is damped and indicates an average-value sound level. The effect of brief sound
peaks is minimized in this position.
WEIGHTING
Set WEIGHTING to weight the sound measurement for a particular frequency range. When set to A, the meter primarily measures frequencies in the 50010,000 Hz range, which is the area of greatest sensitivity to the human ear. When set to C, the meter measures uniformly over the frequency range from 3210,000 Hz,giving an indication of the overall sound level.
MICROPHONE
The meter’s built-in microphone works best when you point it directly at a sound source.
TRIPOD ADAPTER
You can mount the meter on a camera tripod (standard 1/4-20 thread) to eliminate hand noise and minimize the effects of sound reflected from your body. This
makes it easy to use the meter with auxiliary recording or test equipment.
CAL(CALIBRATION)
Your meter has been accurately calibrated at the factory and normally will not require further adjustment. If necessary, an audio professional can use the CAL
hole on the meter with special equipment, including a sound generator, to calibrate it.
MAKING MEASUREMENTS
Important:
• Do not hold the meter directly between you and the sound source, as this might produce an error of several decibels in the frequency range above 100
Hz. Position the meter so an imaginary line between you and the meter is perpendicular to a line between the meter and the sound source.
• Handle the meter carefully . The microphone and meter movement are fragile and might be damaged if the instrument is dropped. Do not operate the
meter at a range setting that causes “pegging” of the needle. This could damage the sound levels.
Follow these steps to select the desired response, weighting, and range.
1. Set RESPONSE to FAST if the sound source you want to measure consists of short bursts or if you want to measure only peak values. Or, set RESPONSE
to SLOW if you want to measure average sound levels.
2. Set WEIGHTING to A if you want to measure noise level or C if you want to measure sound levels of musical material.
3. Set RANGE to the highest setting(120 dB)then adjust it downward until there is significant deflection of the needle.v for the greatest accuracy , always use
the lower of any two possible settings.
For example, if RANGE is set to 80 dB and the meter reads around -5 , reset RANGE to 70 dB so the meter reads +3,for an actual sound level of 73 dB.
Important: For meaningful readings, any particular sound to be measured must be at least 10 dB louder than the background noise level.
While taking measurements, minimize the effect of your body’s presence. When the sound is coming mainly from one direction, the level reading might be
significantly affected by reflections from your body. For the most accurate readings and the best polar response, point the meter’s microphone toward the
sound source when possible.
Sound Level (dB)
Maximum Duration
(A- Weighting, SLOW
Per Day(hours)
CHECKING NOISE LEVELS
response)
This chart, gathered from Federal, state, and local agencies, shows standards for just how
90
8
much noise is acceptable.
Noise is inevitable in almost any environment. Depending on the level and duration, noise can
be a minor irritant, a definite disturbance, or even a threat to your hearing.
To use your meter to check noise levels, set WEIGHTING to A and RESPONSE to SLOW. Take
measurements at several points in the test area, with the meter positioned properly.
CHECKING ROOM ACOUSTICS
92
95
97
100
102
105
110
115
6
4
3
2
1 1/2
1
1/2
1/4 or less
Permissible noise exposures.Extracted from U.S.
The size, shape, and furnishings of a room can have a tremendous effect on a home theater
Department of Labor Noise Regulations.
system’s performance. A “hard” room with bare surfaces tends to exaggerate treble response,
sometimes giving the music a strident quality. A “soft” room with curtains, over-stuffed furniture, carpet, etc. might reduce high-frequency response so the bass
sounds dominant, giving you a “mushy” sound. Dewaves might also develop in the room, giving your system a “peaky,” eccentric response.
The first step in solving this problem is to analyze the room’s acoustics with your meter and a suitable test recording. The test recording should produce pure
tones, one at a time, at intervals spanning the audio spectrum. Make a graph or table showing the sound levels generated by the individual tones. This gives
you a clear idea of the frequency response of your “total system” —home theater equipment and room included.
The next step is to smooth out the reponse. Adjusting tone controls and varying speaker placement might improve the sound significantly. But, to approximate
the ideal, “flat response,” you could add a frequency equalizer to your home theater system. Frequency analyzers, such as the NADY GEQ Series graphic
equalizers or the PEQ-5B parametric equalizer, let you boost or cut response in different ranges, as indicated by your frequency response analysis. Properly
equalized, your system can sound like one costing considerably more!
Note: If WEIGHTING is set to C, the meter’s frequency reponse is flat from 32 to 10,000 Hz ((3 dB). Above 10 kHz, the frequency response of the meter
drops off rapidly. Besure to consider this when you use a test recording that includes tones at the extreme high end of the audio spectrum.
SPECIFICATION
Range:
Switch Setting Range of Measurement
60 dB
50-66 dB
70 dB
60-76 dB
80 dB
70-86 dB
90 dB
80-96 dB
100 dB
90-106 dB
110 dB
100-116 dB
120 dB
110-126 dB
Load Impedance: 10 kohm minimum
Distortion: Less than 2% at 1 kHz, 0.5-volt
Microphone: Electret condenser omnidirectional becoming slightly directional
with increase in frequency
Battery: One 9-volt rectangular type
Accuracy: ±2 dB @ 114 dB
Standard: 0 dB = 0.0002 µbar
Weighting: A and C
Response: Fast and Slow
Signal Output: 1.0 volt (peak) minimum into open circuit, with full-scale meter
deflection at 1 kHz
Battery Check: Tests “good” from 7.0 To 10.5 volts
Expected Battery Life: 110 working hours (alkaline battery)
Size (HWD): 6.25” x 2.43” x 1.75” (160 x 62 x 44 mm)
Weight: 6.6 oz (about 185 grams)
Specifications are typical; individual units might vary. Specifications are subject to change and improvement without notice.
SERVICE
(U.S.) Should your Nady ASM-2 Sound Level Meter require service, please contact the Nady Service Department via telephone at (510) 652-2411 or e-mail to
[email protected] for a Return Authorization (R/A) Number and a service quote (if out of warranty). Make sure the R/A Number is clearly marked on the outside
of the package and enclose a cashier’s check or money order (if not prepaid with a credit card). Ship the unit prepaid to: Nady Systems, Inc., Service
Department, 6701 Shellmound Street, Emeryville, CA 94608. Include a brief description of the problems you are experiencing.
The warranty card enclosed with this system contains additional valuable warranty and service information. Keep it in a safe place for future possible
reference. Do not attempt to service this unit yourself as it will void the warranty.
(International) For service, please contact the Nady distributor in your country through the dealer from whom you purchased this product.
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