Training | Resources

arrow_back_ios

Main Menu

arrow_back_ios

Main Menu

See All Acoustic End-of-Line Test Systems See All DAQ and instruments See All Electroacoustics See All Software See All Transducers See All Vibration Testing Equipment See All Academy See All Resource Center See All Applications See All Industries See All Insights See All Services See All Support See All Our Business See All Our History See All Our Sustainability Commitment See All Global Presence
arrow_back_ios

Main Menu

See All Actuators See All Combustion Engines See All Durability See All eDrive See All Production Testing Sensors See All Transmission & Gearboxes See All Turbo Charger See All DAQ Systems See All High Precision and Calibration Systems See All Industrial electronics See All Power Analyser See All S&V Hand-held devices See All S&V Signal conditioner See All Test Solutions See All DAQ Software See All Drivers & API See All nCode - Durability and Fatigue Analysis See All ReliaSoft - Reliability Analysis and Management See All Test Data Management See All Utility See All Vibration Control See All Acoustic See All Current / voltage See All Displacement See All Load Cells See All Pressure See All Strain Gauges See All Torque See All Vibration See All Power Amplifiers See All LDS Shaker Systems See All Vibration Controllers See All Accessories for Vibration Testing Equipment See All Training Courses See All Articles See All Acoustics See All Asset & Process Monitoring See All Custom Sensors See All Data Acquisition & Analysis See All Durability & Fatigue See All Electric Power Testing See All NVH See All Reliability See All Smart Sensors See All Vibration See All Weighing See All Automotive & Ground Transportation See All Calibration See All Installation, Maintenance & Repair See All Support Brüel & Kjær See All Release Notes See All Compliance See All Our People
arrow_back_ios

Main Menu

See All CANHEAD See All GenHS See All LAN-XI See All MGCplus See All Optical Interrogators See All QuantumX See All SomatXR See All Accessories See All BK Connect / Pulse See All API See All Microphone Sets See All Microphone Cartridges See All Acoustic Calibrators See All Special Microphones See All Microphone Pre-amplifiers See All Sound Sources See All Accessories for acoustic transducers See All Experimental testing See All Transducer Manufacturing (OEM) See All Accessories See All Non-rotating (calibration) See All Rotating See All CCLD (IEPE) accelerometers See All Charge Accelerometers See All Impulse hammers / impedance heads See All Cables See All Accessories See All Electroacoustics See All Noise Source Identification See All Environmental Noise See All Sound Power and Sound Pressure See All Noise Certification See All Industrial Process Control See All Structural Health Monitoring See All Electrical Devices Testing See All Electrical Systems Testing See All Grid Testing See All High-Voltage Testing See All Vibration Testing with Electrodynamic Shakers See All Structural Dynamics See All Machine Analysis and Diagnostics See All Dynamic Weighing See All Calibration Services for Transducers See All Calibration Services for Handheld Instruments See All Calibration Services for Instruments & DAQ See All On-Site Calibration See All Resources See All Software License Management

Leq and SEL - When to choose what? 


Leq and SEL are energy parameters which provide a very useful means of describing fluctuating sounds. In this application note we will look at what Leq and SEL are; What is the difference between between them, and when do we use them?
slm-icon-3-2245
FROM SIMPLE TO ADVANCED
B&K SOUND LEVEL METERS

What are Leq and SEL?

Equivalent Continuous Sound Level (Leq )

Leq (equivalent continuous sound level) is defined as the steady sound pressure level which, over a given period of time, has the same total energy as the actual fluctuating noise. Thus, the Leq is in fact the RMS sound level with the measurement duration used as the averaging time.

Assessing a fluctuating noise level means getting a value for a level that is, in simple terms, the average level. Leq is defined as the steady sound pressure level which, over a given period of time, has the same total energy as the actual fluctuating noise. It is also known as the equivalent continuous sound level, or the time-averaged sound level.

Sound Exposure Level (LAE or SEL)

An alternative energy parameter is the sound exposure level - LAE or SEL - a logarithmic measure of the sound exposure of a sound relative to a reference value. It is similar to the Leq as the total sound energy is integrated over the measurement period. However, instead of averaging over the measurement period, a reference duration of 1 second is used.

Leq can be measured directly with a professional sound level meter, if an A-weighting filter is used. This is it is expressed as LAeq, the measurement of the equivalent continuous sound level using the A-weighted filter network.

 

When to use Leq and SEL?

Let us look at some typical cases which illustrate when a clearer answer can be easily obtained by using an Sound Level Meter.

 

Leq Measurements

When measuring Leq the choice of measurement duration depends on the type of noise.

Fluctuating Machinery Noise

Fluctuations in machinery noise can make it difficult to put a value on the noise level. It can be even more difficult if the machine has a complex working cycle. The reason for the measurement uncertainty is that the analogue sound level meter does not provide time constants which are of sufficient duration. However, this can be overcome by measuring the overall energy of the noise.

For relatively steady noises such as machinery noise, the reading can be taken when the display of the instrument has stabilized. With cyclical noise, the measurement period should include an integer number of cycles so that an Leq measurement effectively represents the true average SPL, having the same energy as the fluctuating sound.

Long-term Noise Exposure

It is often necessary to rate noise on a long-term basis. In industry, workers’ exposure to noise during work is assessed to establish its acceptability.

In towns and dwellings, environmental noise produced by traffic, industry, etc., is measured to estimate annoyance caused by noise and thereby the degree of community reaction to be expected. In both cases, noise may vary considerably over the exposure period. Recordings of a time-varying RMS do not allow either direct comparison or simple rating of noise exposure. 

Leq measurements for long-term exposure rating, require the selection of representative measurement periods. In the case of occupational noise exposure, this may be a whole working day, or alternatively parts of the day in which representative measurements of the entire working day can be made.

Similarly, community noise exposure can be assessed by measurement of Leq over a whole day, or by taking ‘period’ Leq measurements of representative intervals within typical periods (for example, quiet periods during the daytime, rush hours, evening, night).

 

LAE (SEL) Measurements 

LAE (SEL) is numerically equivalent to the total sound energy, whereas Leq is proportional to the average sound power. Leq measurements give us very useful results in many situations. However, an Leq measurement does not remove ambiguity in the case of transient noise, for example, from an aircraft fly-over or a vehicle pass-by.

Transient Noise

These situations often result in wide variations from background noise to the maximum level and if only the maximum level is reported, information on the duration of the noise (an important feature for rating annoyance) is lost. This also makes it difficult to compare between rapid and slow events and to combine different events for noise prediction purposes.

Since Leq is an energy average, only the highest levels (from the maximum to, say, 15 to 20 dB below it) contribute significantly to the total energy. Hence, if a measurement begins and ends in the background noise, the resulting Leq will depend on the measurement period, even though the total energy is the same.

In such a case, the use of an LAE (SEL) eliminates the influence of the measurement duration. Although the total sound energy is integrated over the measurement period – as with Leq – instead of then averaging this over the measurement period, a reference duration of 1 s is used.

Modern Slavery Statement     Imprint    Cookie Policy    Privacy Policy    Sitemap    Ethical Business

 

 

© 2024 Hottinger Brüel & Kjær

 

 

close
nCode logo
Graphics Brand

We have moved ${referer} to www.hbkworld.com

 

This will bring together HBM, Brüel & Kjær, nCode, ReliaSoft, and Discom brands, helping you innovate faster for a cleaner, healthier, and more productive world.

close
ReliaSoft-Logo-webp
Graphics Brand

We have moved ${referer} to www.hbkworld.com

 

This will bring together HBM, Brüel & Kjær, nCode, ReliaSoft, and Discom brands, helping you innovate faster for a cleaner, healthier, and more productive world.

close
Prenscia HBM-Logo rgb
Graphics Brand

We have moved ${referer} to www.hbkworld.com

 

This will bring together HBM, Brüel & Kjær, nCode, ReliaSoft, and Discom brands, helping you innovate faster for a cleaner, healthier, and more productive world.

close
HBM-Logo blue rgb
Graphics Brand

We have moved ${referer} to www.hbkworld.com

 

This will bring together HBM, Brüel & Kjær, nCode, ReliaSoft, and Discom brands, helping you innovate faster for a cleaner, healthier, and more productive world.

close
logo of Brüel & Kjær (BKSV), experts of sound and vibration measurements from HBK
Graphics Brand

We have moved ${referer} to www.hbkworld.com

 

This will bring together HBM, Brüel & Kjær, nCode, ReliaSoft, and Discom brands, helping you innovate faster for a cleaner, healthier, and more productive world.