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LED-noise-testing has become a complex process

From 15 Minutes to 8 Hours: New Noise Testing for Light Bulbs

Written by Randy Abernathy on . Posted in Lighting

For lighting manufacturers, ENERGY STAR® requirements have always been a moving target.

The latest ENERGY STAR Lamps Specification V1.0 is combining and replacing two separate specifications for CFL and LED bulbs with one technology neutral specification. In this new specification, manufacturers are allowed to conduct noise tests themselves.

The allowed audible noise level for a bulb hasn’t changed – but the detail involved in testing has. As of October 1, 2014, all dimmable bulbs must pass the new Noise Test and be qualified to the new Lamps specification if they carry the ENERGY STAR label.

This new testing regimen is a lot more complex and a lot more expensive than before, and most manufacturers don’t have the capacity to do it right.

Why Noise Matters

Why does ENERGY STAR care about noise? It’s not a measure of energy efficiency. Noise does, however, influence consumer adoption of the product.

ENERGY STAR’s mandate is to get consumers to use environmentally friendly products, and most consumers are not going to tolerate lighting that gives off an annoying buzz. Remember the reaction to CFL bulbs, and how fast the negative word spread?

The color was terrible, the buzz was annoying, they burned out too quickly, they didn’t work with dimmers, sometimes they gave off smoke when they burned out … the EPA doesn’t want similar bad buzz – so to speak – about LEDs.

The Old Test

Under the old specifications, the test was very simple. A quiet environment was required for the test and the only measuring equipment needed was a noise meter. A bulb was placed on a table, a noise meter was placed a few feet away, and the light bulb was turned on. The bulb was allowed to warm up for about an hour and finally the noise level was measured on all sides. That was it – six simple measurements.

The New Test

Under the new ENERGY STAR Lamps Specification, manufacturers can now perform the noise testing themselves. One challenge, though, is creating a testing environment that is quiet enough, while also having the measuring equipment required for this new test.

To do this test properly, a room with an ambient noise level <20 dBA – much quieter than a normal office environment – is needed. For reference, the ambient noise in a library is around 20 to 24 dBA. Anything producing sound louder than 24 dBA is easily heard over the ambient noise; anything quieter would likely not be noticed. Normal conversation at 3ft. is about 60-65 dBA.

A lot of time is also required to complete this test – maybe even a bigger challenge. The new test requires:

  • Testing on dimmers, which the old test did not require
  • Testing multiple bulbs on one dimmer, and
  • Testing bulbs on multiple dimmers of different design

Lighting Standards

Find out more information on the various requirements and standards for lighting products.


Here’s how the new test works:

  1. Measure the light level in one-minute increments until the light reading from one minute to the next doesn’t change more than 0.5%. Then it’s considered stable. In some cases this can take up to 45 minutes.
  2. Take noise measurements at six points around the bulb: On all four sides, 90 degrees apart, plus above and below.
  3. Add a dimmer to the circuit, set the bulb to maximum brightness, do the stabilizing process all over again, and measure the noise again at six points around the bulb.
  4. Dim the bulb, stabilize it, and measure noise again.
  5. Repeat steps 3 and 4 with four lights on the dimmer.
  6. Then change the dimmer, go back and do it all again.
  7. This process is repeated until noise has been measured on at least 5 different dimmers.

It’s clear to see how what used to take as little as 15 minutes can now take from 8 to 12 hours, and why the price of testing has increased significantly.

Testing the noise level of light bulbs has become a very complex and exacting process, and not one most manufacturers have the time – or the facilities – to complete. October 1st is coming fast, and partnering with a third-party test lab is the best way to make sure your lighting products are in compliance by the deadline.

Randy Abernathy

Randy Abernathy

From its founding in 2001, ACS has distinguished itself in the compliance testing industry with the caliber of its people, the depth of their experience, and their shared commitment to delivering exceptional service and results. As Manager of Certifications Programs and Quality Assurance, Randy Abernathy ensures that ACS meets and exceeds our own high standards, streamlining the certifications process for customers. Randy joined the ACS team in 2007, bringing over two decades of intensive industry experience with him. After earning a diploma in Electronics Technology from North Georgia Technical College in 1983, he took a job with the Rockwell International Missile Systems Division. He spent his days as a Test Technician and his nights as a student.READ MORE