Sound Meter Measurements

The Taylor sound meter measures the sound generated by a textile when it is drawn over glass pins. 

Field Light, sound meters measurements tape measures Ambient environment workstation dimensions... 

The second aspect is the proposed novel Inferential Transmission Loss method (InTLM) in determining TL using 2-microphone impedance tube. The approach is a modification to the usual transfer method that infers transmission coefficient with and without the rigid wall. The calculated results showed high accuracy from —0.2 to -3.2 dB compared with sound meter measurements. Thus, the InTLM can be applied for 100 mm diameter specimens which use the large tube in estimating the TL without the need to use 4-microphone impedance tube... 

Different laboratories use different criteria for determining whether a drop-test resulted in an explosion ( go ) or failure ( no-go ). In many test facilities any visual observation of smoke, flash or flame, or any crackle, pop or bang detected by the operator is taken to signify a go result. Sometimes sound-meters are used to detect the audible signals of a drop test. In still more elaborate tests, the volume of gas, produced by a go result, is measured. In general, for sensitive explosives like PETN, distinguishing between go ... 

The sound meter was not able to measure completely the sound going in three directions hence, the sound intensities in each direction could not be directly compared. However, regarding an analysis based on a reduced distance (the difference in a frequency component caused by distance and direction), it may be understood in the following manner ... 

Exposure monitoring is another element of HCP. The sound level and exposure time should be measured. It is very important that sound levels measured are typical of those encountered by the worker. Proper survey techniques include sound-pressure-level (SPL) meters that should be vigorously apphed at monitored workplaces. They measure the smallest pressure changes initiated by the vibrating source and transmitted through the air. 

Using a sound meter, the fiillowiog measurements were made for the fellowii sources Rock band at a concert (100 X 10 /tPa), a Jack hammer (2 X 10 juPa), and a whisper (2000 /uPu). Convert these readings to dB values. 

One of the drawbacks of the two-microphone transfer function method is that the absorption coefficient determined may not be a true representation of the material s characteristic. In the case of a porous material, such as silica aerogels, the reflected wave from the rigid wall could contribute to a rise in the absorbed energy by the material. To account for this uncertainty, the four-microphone impedance tube setup is usually used to determine the transmission loss (TL) and absorption coefficient (Feng 2013). In the absence of additional microphones downstream of the specimen, a sound meter could be used instead to measure the TL of the specimen under test. However, the sound meter picks up discrete transmitted signals at periodic interval, which could result in a mismatch with the generated signals from the source. 

Fig. 7.3 Schematic of InTLM experimental setup for transmission loss measurement using 2-miciophone and sound meter without the rigid wall backing...

The new OHD/Cirrus Research Optimus RTA Sound Level Meter measures all data in one measurement this includes the entire 120dB dynamic range. Just press three buttons, and you re done. Voice tag allows you to audibly notate the measurement, which means no need for keeping track of a log sheet. Tbe Optimus is small, lightweight and incredibly easy to use. Occupational Health Dynamics, www.ohdusacom/products/ sound level meters/optimus.php. Cnvfe 307... 

Sound level meters measure noise only at a given point at the time of observation. If the noise being measured is constant in both space and time, meters will give an accurate representation of the situation. However, if the sound level changes with time and location (for instance, as an operator moves around), it will be necessary to record either the sound level manually using short time intervals (5 to 10 s) or the noise data for later analysis of the time history of the noise. The second approach is preferable when a worker s noise exposure is related to duty cycles or product flow. In this case, extrapolations can be made on the basis of total day production to determine the noise exposure of an employee over a full day. 

Alarm Notification/Remote Monitoring OTHER METERS Microwave Leakage Detectors Frequency Counters Sound/Noise Measurements CONCLUSION... 

When screening for noise exposures, sound level meter measurements and estimates of exposure duration are sufficient. Spot readings over 80 decibels from a sound level meter is generally sufficient for a more complete evaluation. OSHA provides technical specifications and procedures for measuring environmental noise. Sites where noise protection is required should be marked with a sign (Figure 4-5)... 

Preformed or molded earplugs should be individually fitted by a professional. When properly inserted, they work as well as most molded earplugs. The individually fitted earplugs are fitted by a professional because they are only for a specific task determined with a sound level meter measured at a slow response. Due to a worker s mobility, personal monitoring is conducted by the use of a noise dosimeter. 

The noise exposure of employees shall be detennined by measuring the sound levels with a sound level meter measured on the A scale at slow response. Where area monitoring is not feasible (due to worker mobility, etc.) personal monitoring by use of a noise dosimeter shall be conducted. 

Several characteristic parameters and measurements apply to sound and noise. A source s sound intensity, measured in joules per square meter per second or watts per square meter, is the average rate at which sound energy is transmitted through a unit area that is normal to the direction the sound is traveling. Sound intensity is commonly expressed by its level, usually in terms of 10" watts/m. Sound pressure refers to the root-mean-square values of the pressme changes above and below atmospheric pressure, which are used to measure continuous noise. Soimd pressure is measured in Newtons per square meter (N/m ) or pascals (Pa), where 1 N/m = 1 Pa. 

Since sound intensity meters can differentiate between the active and reactive sound fields, measurements of intensity taken close to noise somces can faithftiUy indicate the radiated sotmd energy. However, using a conventional sound level meter near to a noise source may indicate higher sotmd power levels than occur in the far field because these instruments cannot differentiate between active and reactive fields. 

Noise monitoring is usually located in the HASP as part of the monitoring program. Noise monitoring should be performed in accordance with acceptable practices. Typically, noise levels are monitored in the field with either a Type I or Type II sound level meter (SLM). Noise dosimeter readings can also be obtained to determine the percent (%) noise dose. Noise levels and % doses measured are then compared to limits listed in OSHA standard 29 CFR 1910.95, Hearing Conservation [3]. 

The sensor is the element of an instrument directly influenced by the measured quantity. In temperature measurement the thermal mass (capacity) of the sensor usually determines the meter s dynamics. The same applies to thermal anemometers. In IR analyzers used for concentration measurement, the volume of the flow cell and the sample flow rate are the critical factors. Some instruments, like sound-level meters, respond very fast, and follow the pressure changes up to several kHz. 

Weighting A The frequency-selective device on a sound level meter used to measure the A frequency network. 

Sound intensity is a measure of energy, and its units are watts per meter. Intensity is proportional to the square of pressure ... 

The simplest sound level meter consists of a microphone, an amplifier and a meter of some type. Sound level meters are graded according to British and international standards, and the most common type used for accurate measurement purposes it known as the Precision Grade or Type 1 meter. In practice, a basic sound level meter will incorporate weighting networks with either in-built octave filters or provision for connecting an external filter set (Figure 42.6). 

Portable sound level meters are also available which can measure percentiles. These either hold the results in a memory which can be separately interrogated or may be connected to a computer for a printout. Larger machines (known as environmental noise analyzers) are available which can record percentiles and Leq readings and produce a printout. These are resistant to weather and can be left on-site for up to a week. 

In practice, measurements are made with the use of an accelerometer. This device is connected to a sound level meter and may make measurements of acceleration in terms of decibels (or by changing scales or use of a device similar to a slide mle, in direct terms). An integrator can be connected between the accelerometer and the meter to express the results in terms of velocity or displacement. 

---