Simpson 884-2 Manual de usuario

Simpson Model 884-2

Sound Level Meter

OPERATOR’S MANUAL

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About this Manual

To the best of our knowledge and at the time written, the information contained in

this document is technically correct and the procedures accurate and adequate

to operate this instrument in compliance with its original advertised specifica-

tions.

Notes and Safety Information

This Operator’s Manual contains warning symbols which alert the user to check

for hazardous conditions. These appear throughout this manual where appli-

cable, and are defined below. To ensure the safety of operating performance of

this instrument, these instructions must be adhered to.

Warning, refer to accompanying documents.

Caution, risk of electric shock.

This instrument is designed to prevent accidental shock to the operator when

properly used. However, no engineering design can render safe an instrument

which is used carelessly. Therefore, this manual must be read carefully and com-

pletely before making any measurements. Failure to follow directions can result

in a serious or fatal accident.

Warranty and Returns

SIMPSON ELECTRIC COMPANY warrants each instrument and other articles

manufactured by it to be free from defects in material and workmanship under

normal use and service, its obligation under this warranty being limited to making

good at its factory or other article of equipment which shall within one (1) year

after delivery of such instrument or other article of equipment to the original

purchaser be returned intact to it, or to one of its authorized service centers, with

transportation charges prepaid, and which its examination shall disclose to its

satisfaction to have been thus defective; this warranty being expressly in lieu of

all other warranties expressed or implied and of all other obligations or liabilities

on its part, and SIMPSON ELECTRIC COMPANY neither assumes nor autho-

rizes any other persons to assume for it any other liability in connection with the

sales of its products.

This warranty shall not apply to any instrument or other article of equipment

which shall have been repaired or altered outside the SIMPSON ELECTRIC

COMPANY factory or authorized service centers, nor which has been subject to

misuse, negligence or accident, incorrect wiring by others, or installation or use

not in accord with instructions furnished by the manufacturer.

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Contents

1. INTRODUCTION ............................................................................... 7

1.1 General Description ........................................................................... 7

1.2 Specifications ..................................................................................... 7

1.3 Items And Accessories Furnished With Instrument ............................ 9

1.4 Available Accessories ........................................................................ 9

2. INSTALLATION .................................................................................. 9

2.1 Unpacking And Inspection ................................................................. 9

2.2 Shipping ...........................................................................................10

2.3 Service ..............................................................................................10

2.4 Battery Installation Or Replacement ................................................10

2.5 Installation ........................................................................................10

2.5.1 Tripod or Strap Mounting .................................................................. 10

2.5.2 Accuracy Of A Measurement .......................................................... 10

2.6 Care ..................................................................................................10

3. APPLICATION ................................................................................. 11

3.1 Decibel Scale ...................................................................................11

3.2 Measurement And Exposure Standards ..........................................11

3.3 Sound Fields .................................................................................... 12

3.3.1 Free Field .......................................................................................... 12

3.3.2 Reverberant Field ............................................................................. 12

3.3.3 Semi-Reverberant Field ................................................................... 13

3.4 Microphone Orientation ....................................................................13

3.5 Effect Of Operator's Presence ..........................................................13

3.6 Windscreen .......................................................................................14

3.6.1 Loss of System Sensitivity Due to Windscreen .............................. 14

3.7 Meter Fluctuations ............................................................................14

3.8 Background Noise ............................................................................14

3.9 Dual Sound Sources ........................................................................ 15

4. OPERATING INSTRUCTIONS ......................................................... 16

4.1 Precautions .......................................................................................16

4.2 Operational Items And Features ...................................................... 16

4.3 Sound Level Measurements ............................................................18

4.4 Use With Auxiliary Equipment ..........................................................18

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1. INTRODUCTION

1.1 General Description

The Simpson 884-2 Sound Level Meter (hereafter referred to as the 884-2 or the

Instrument) is a portable, general purpose sound level instrument, capable of

accurate sound level measurements over a range of 40 to 140 dB. This encom-

passes the noise level of a quiet residence to that beyond the threshold of pain.

This dB range is compatible with current Federal, State, and local noise ordi-

nance requirements; including safety and environmental noise checks.

The 884-2 meets the requirements of the American National Standards Institute

(ANSI) Standard Specification S1.4 - 1983 for "Type S2A General Purpose Sound

Level Meters and the International Electro- Technical Commission (IEC) 651." It

can be used by industry to measure noise levels to comply with Occupational

Safety and Health Act of 1970 (OSHA) and the Walsh-Healy Act, except for direct

measurement of impact (impulse) noise.

The 884-2 can be hand-held for rapid testing or mounted on a tripod for measure-

ments over extended periods of time. The meter case is constructed of high-

impact molded plastic, especially contoured at the microphone end to minimize

reflections of the sound energy field being measured.

The 884-2 is equipped with a range selector switch which references the 0 dB

point of the indicating instrument to the range selected. For example, when the

range switch is set to 70, the zero (0) mark on the black arc is equal to 70 dB. Fast

or slow meter response is switch selectable.

The 884-2 offers three outputs which are proportional to the sound level input: a

RMS output, a dB output, and an external filter output that is compatible with the

Simpson 898 Octave Band Filter.

1.2 Specifications

The specifications for the 884-2 are listed in Table 1-1.

Table 1-1. Specifications

1. Microphone: The microphone is a condenser type with the size as

type L per ANSI S1.12-1967. The nominal electrical

impedance is 350V, 20% @ 23°C. The microphone is

omnidirectional; its angle of incidence which approxi-

mates random incidence response is 70°.

2. Sound Level: Measurement Ranges: 40 dB to 140 dB. Zero (0) dB

reference is 20 μPascals. :Maximum SPL: 140 dB SPL

for linearity within 1 dB.

3. Accuracy: Meets ANSI S1.4-1983 for a Type S2A instrument.

4. Weighting: Conforms to the A-weighting characteristic specified

in ANSI S1.4-1983. The "External Filter" jack may be

used to obtain a flat response.

5. Meter: Pivot and Jewel movement with 2-1/2" dial having

end markings of –10 dB and +10 dB, and fifteen 1 dB

scale markings. From –5 dB to +10 dB the accuracy

specification for a Type S2A instrument.

6. Speed of Response:

Types of response: Selectable "Slow" or "Fast" modes provide the

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response times required by the ANSI specification for

a Type S2A instrument.

SLOW Response: Response to a 500 millisecond tone burst of 1000 Hz

is nominally 2.5 dB down from a reference steady

state signal at the same level and frequency. Over-

shoot response to a suddenly applied steady state

signal is less than 0.5 dB. When an applied signal is

tuned off, the decay rate is less than 3 seconds per 10

dB.

FAST Response: Response to a 200 millisecond tone burst of 1000 Hz

is nominally 2.0 dB down from a reference steady

state signal at the same level and frequency. Over-

shoot response to a suddenly applied steady state

signal is less than 0.5 dB. When an applied signal is

tuned off, the decay rate is less than 0.5 seconds per

10 dB

7. Linearity: Primary indicator range is from 0 dB to +10 dB on

each range. Overall indicator range is –5 dB to +10

dB. The dedicated "OSHA" range primary indication

is +105 dB to +115 dB, with an overall indication of

+100 dB to +115 dB. Within these limits, the primary

indicator accuracy is 1 dB and the overall accuracy is

1.5 dB.

8. Calibration: Recommended calibration frequency is 1000 Hz at

sound pressure levels of either 94 dB on the 90 dB

range, or 114 dB on the 110 dB range. Screwdriver

adjustable from the side of the case.

9. Output Connections: This Instrument is provided with three outputs: Exter-

nal Filter, RMS Output, and dB Output.

External Filter: Provides non-weighted (flat response) output of 120

mV RMS, at meter reading of +10 dB, into a 100 KV

load; a lower impedance may affect the meter read-

ing. This output is not affected by the "Fast-Slow" set-

ting. The recommended plug is Switchcraft's #750

(0.141" diameter).

RMS Output: Provides weighted or non-weighted output of 1.00 V

RMS, at a meter reading of +10 dB, into a 100 KV

load; a lower impedance will not affect the meter read-

ing. This output is not affected by the "Fast-Slow" set-

ting. The recommended plug is Switchcraft's #850

(0.097" diameter).

dB Output: Provides logarithmic output of +1.50 V DC, at a meter

reading of +10 dB, into a 100 KV load; a lower imped-

ance will not affect the meter reading. The response

time of this output is set by the "Fast-Slow" setting. The

exponential-time-averaging time constant is per ANSI

S1.4-1983, paragraphs 6.2 and 6.3: Slow is 1000

milliseconds, and Fast is 125 milliseconds. The rec-

ommended plug is Switchcraft's #850 (0.097" diam-

eter).

10. Power

Requirements: One 9-volt alkaline battery, NEDA 1604A (or equal)

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will typically provide 40 hours of continuous opera-

tion.

11. Temperature

Range: Operating temperature is –10°C to +50°C.

Storage

Temperature: –40°C to +60°C with the battery removed.

12. Temperature

Influence: Typically 0.015 dB/°C at 1kHz.

13. Operating Humidity: 0 to 90% relative humidity (non-condensing) for

a reading change of < 0.5 dB.

14. Warm-up Time: Approx. 30 seconds.

1.3 Items And Accessories Furnished With Instrument

All items required to operate the 884-2 are furnished with each Instrument, and

are listed in Table 1-2.

Table 1-2. Accessories Furnished with Instrument

Qty. Description Part Number

1 9-volt battery NEDA 1604A*

1 Operator's Manual 6-115307

*Available from local retail stores.

1.4 Available Accessories

Table 1-3. Available Accessories

Description Part/Catalog Number

Screwdriver 5-116470

Windscreen 00197

Calibrator, 890-2 12890

Package Case 10-866065

Adapter, Microphone to Tripod 00184

898 Octave Band Filter Set 02231

2. INSTALLATION

This section contains information and instructions for the packaging and ship-

ping of the 884-2. Included are procedures for unpacking and inspection, service,

shipping, battery installation, installation and care.

2.1 Unpacking And Inspection

Examine the shipping carton for obvious signs of damage. If shipping carton is in

good condition, inspect the Instrument for possible damage incurred during ship-

ment. If damaged, notify the carrier and supplier and do not attempt further use of

the Instrument. If the Instrument appears to be in good condition, read the Operator's

Manual in its entirety. Become familiar with the Instrument in the manual, then

proceed to check the electrical performance as soon as possible. Save the ship-

ping carton and packing materials for future storing or shipping of the Instrument.

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2.2 Shipping

Pack the Instrument carefully and ship it prepaid to the proper destination. Insure

the Instrument.

2.3 Service

This Instrument contains no operator serviceable parts, except for the battery.

Refer all service requests to the Simpson factory. If the Instrument is covered by

warranty, include the model number, serial number, and date of purchase.

2.4 Battery Installation Or Replacement

The 884-2 is powered by a 9-volt alkaline battery. The battery is packaged sepa-

rately. To install or replace the battery:

a. Turn the range switch to the "OFF" position.

b. Using a screwdriver or coin, loosen the two screws located on the battery

cover access compartment and remove the cover.

c. Install or replace the battery with the connector on the left side of the Instru-

ment. Route the cable between the battery and upper wall of the battery

compartment.

2.5 Installation

The Instrument, when in operation, may be either hand-held or mounted on a

tripod. The physical position of the Instrument does not affect the accuracy.

2.5.1 Tripod or Strap Mounting

The 884-2 can be attached to any commercial, photography-type tripod having a

standard 1/4-20" mounting screw. The mounting screw is aligned with the threaded

insert in the case and finger-tightened. A camera-type carrying strap can be

attached to the threaded insert. Carry the Instrument with the strap around the

wrist to prevent accidental dropping.

2.5.2 Accuracy Of A Measurement

The accuracy of a measurement will be affected by several factors, one of which

is the position of the microphone with respect to the sound source. Read Section

3 carefully for general background information. (See Section 4 for operating in-

structions for obtaining correct data from the measurements.)

2.6 Care

a. Immediately clean any spilled materials from the Instrument and wipe dry. If

spillage is corrosive, use a suitable cleaner to remove it and to neutralize

corrosive action.

b. To protect the microphone, keep sharp objects away from the top. Never rest

the unit on the microphone. If the microphone is detached, always lay it on its

side.

c. Whenever the Instrument is not in use, set the range switch to the OFF posi-

tion.

d. Avoid prolonged exposure or usage in areas subject to temperature and

humidity extremes, vibration, mechanical shock, dust, corrosive fumes, and

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strong electrostatic and electromagnetic interference.

e. Verify Instrument calibration with a 890-2 Acoustical Calibrator.

f. It is recommended that the Instrument be returned to the factory annually

(sooner if required) for a complete overall check, adjustment, and calibra-

tion.

g. When the Instrument is not in use store it in a room free from temperature

extremes, dust, corrosive fumes, mechanical vibration or shock. If storage

time is expected to exceed 30 days, remove the battery.

3. APPLICATION

This section contains basic information required for effective application of the

884-2 Sound Level Meter, and must be understood before attempting to operate

the Instrument for the first time.

3.1 Decibel Scale

The human ear has a mid-frequency dynamic sound sensitivity range of greater

than one million to one, from the lowest level that can be detected to the highest

that can be tolerated without pain. Because of the large ratio of value involved, a

linear meter scale marked in pressure units becomes impractical. A scale based

on logarithms, called a decibel (dB) scale, is used. This scale expresses the ratio

between the sound pressure level being measured and a reference. This simpli-

fies notation and manipulation by reducing large ratios into smaller convenient

numbers. For example, a million-to-one pressure ratio can be expressed on a 0 to

120 dB scale.

3.2 Measurement And Exposure Standards

The American National Standards Institute (ANSI), in collaboration with scientific

and engineering societies, has established a standard, S1.4-1983, for conform-

ance of all approved sound level meters. Federal, state and local governments

–5

–10

–35

–30

–15

–20

–25

–40

–45

–50

20 50 100 200 500 1000 2000 5000 10,000 20,000

FREQUENCY RESPONSES

FOR SLM WEIGHTING

CHARACTERISTICS

FREQUENCY (Hz)

RELATIVE RESPONSE DECIBELS

BAND C

Figure 3-1. A, B, and C Weighted Responses of the Sound Level Meter

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also have defined allowable noise (undesirable sound energy) level exposure

limits for persons in industrial environments. Selected and applicable parts of

those currently in force are cited in this manual. Standards and government regu-

latory laws are subject to modification or expansion. Check for latest available

documents and information.

The specification for a Type S2A instrument takes into account the average re-

sponse of the human ear which varies as a function of the intensity of sound. It

groups intensity into three weighting curves: "A", "B" and "C". The "A" weighted

curve more closely corresponds to the human ear at the low sound levels.

As indicated in Figure 3-1, the "B" and "C" weighting curves include more of the

low frequency information. Thus, at any level, measurements taken with various

weightings can be compared in determining the frequency content of the noise.

This is done by indicating the level in dB, accompanied by the weighting letter

notation "A", "B" or "C", preferable in parenthesis; e.g., the 100 dB(A), etc.

The allowable employee noise level exposure limits are established by the Oc-

cupational Safety and Health Act of 1970 (OSHA), the Walsh-Healy Act (Federal

and Health Standards (Federal Register, Vol. 36, No. 105, May 29, 1971) and the

OSHA Hearing Conservation Program Amendment, Federal Register, Vol. 46,

No. 162, August 21, 1981. Table 3-1 summarizes these limits.

*Table 3-1. Permissible Noise Exposure Limits

Duration per Day Sound Level, dB(A) SLOW

In Hours Response

32 80

16 85

8 90

6 92

4 95

3 97

2 100

1-1/2 102

1 105

1/2 110

1/4 or less 115

*From Federal Register, Vol. 46, No. 162, August 21, 1981.

3.3 Sound Fields

3.3.1 Free Field

A free field contains no reflecting objects. Ideally it prevails around a point sound

source located in free space. However, it can be considered to exist whenever the

sound level being measured is caused mainly by sound waves coming directly

from the sound source. This can occur even if there are reflecting objects, if

measurements are made close to the sound source.

3.3.2 Reverberant Field

A reverberant field contains reflecting objects and the sound level being mea-

sured is caused mainly by reflections of the sound source. This usually occurs at

a moderate distance from the sound source.

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3.3.3 Semi-Reverberant Field

This field is most common and exists whenever the sound level being measured

contains a significant amount of both reflected and direct sound waves.

3.4 Microphone Orientation

When making measurements in a free or semi-reverberant field, orient the micro-

phone so that the angle of incidence, formed by incoming sound waves and axis

of the microphone, is equal to the random incidence angle of the microphone. For

the 884-2 this angle is 70° (refer to Figure 3-2).

When making measurements in a reverberant field, orientation of the micro-

phone is not critical. However, it is recommended, where possible, that the opera-

tor use the same orientation (70°) as for the free or semi-reverberant field.

Vertical orientation of the microphone is not critical except where it is in line with

a second sound source or a high-amplitude reflection of a sound source. It usu-

ally is invalidated by a second sound source, or by a nearby reflecting surface.

When evaluating a particular sound source, avoid holding the microphone in

such a way that the reading is invalidated by a second sound source, or by the

proximity of a nearby reflecting surface.

3.5 Effect Of Operator's Presence

When sound is coming mainly from one

direction, the reading might be affected

by the relative positions of the microphone

and operator. For example, if the operator

and microphone are in line and facing

the sound source, there can be a marked

increase in response at high frequencies

because the operator will act as a reflec-

tor and produce errors of several dB at

frequencies above 100 Hz. A more uni-

form frequency response is obtained with

the Instrument extended as far as conve-

niently possible in front of the operator,

and the axis of the microphone oriented

to form an angle of incidence of 70° with

the incoming sound wave. Do not point

the Instrument toward a source of noise

other than the one being measured.

The 884-2 (or its microphone) can be

mounted on a tripod for further reduction

in the effects of the operator's presence.

A practical arrangement is to tilt the mi-

crophone axis at an angle of approxi-

mately 45° to 70° with respect to the hori-

zon. This allows the operator to step back

several feet or completely away and still

be able to make measurements.

PLANE OF

MICROPHONE SOUND SOURCE

AXIS OF

MICROPHONE

INCOMING

SOUND WAVE

ANGLEOF

INCIDENCE (70˚)

PLANE OF

MICROPHONE

AXIS OF

MICROPHONE

VERTICAL ANGLE

(45˚ –70˚)

Top View

Side View

Figure 3-2. Orientation of

Microphone and Operator with

respect to Incoming and Sound

Waves

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