100 Things #41: Easily Measure Headphones to EN 50332 with a Pre-written Sequence

We provide many pre-written sequences for testing to standards across many applications, including a suite of sequences testing to the EN 50332 Standard. This test suite consists of two parts to accurately measure the device and included headphones, together and separately. All of the sequence development work has been done, saving your hours of sequence writing. These sequences also include operator instructions, making headphone adjustments on a head and torso simulator easy. You can test in confidence knowing this sequence suite includes everything you need to get up and running fast.

Easily Measure Headphones to EN 50332 with a Pre-written Sequence

Try EN 50332 for yourself

We offer two sequences testing to the EN 50332 standard: EN 50332-1 and EN 50332-2. These sequences are pre-written and ready to run.

Video Script:

Did you know we offer a test sequence for measuring headphones headphones and earphones associated with portable audio equipment to the European standard, EN50332?

This standard specifies the maximum sound pressure level and input / output voltage measurements for portable audio playback devices. These characteristics are usually evaluated at the design and engineering stage as compliance is mandatory in many countries.

Our off-the-shelf test sequence saves hours of development time, and ensures that measurements  are correctly made.

The standard consists of two parts.

Part 1 measures the portable music players together with the headphones they are bundled with. In this measurement, we load an IEC 268 weighted pink noise stimulus file onto the portable device and play it through the earphones at maximum volume. 

The earphones are positioned on a head and torso simulator, or HATS. We record the signal from each ear, and a 1/3rd octave curve is analyzed. A-weighting and free field correction for the HATS are applied, the values between 20 Hz and 20 kHz summed, and the A-weighted equivalent sound pressure level is calculated.

The sequence runs 5 times, with the headphones repositioned between each measurement to average out any variability in the fit and sealing of the device under test. We average these measurements to calculate the final LA eq values.

In part 2, the portable device and the headphones are measured separately. 

To test the music player, we load a weighted pink noise stimulus file onto the portable device and play it through the headphone jack connected to a 32 ohm load at maximum volume. The RMS voltage is averaged over 30 seconds, and the result must be less than 150 mV.

The headphone test is a little more complex. We connect the headphones to an amplifier with less than 2 ohms output impedance. The amplifier’s outputs are split, connecting one side to the headphone and the other directly to the audio interface. This lets us measure the voltage at the headphone while the amplifier is under load. You can see here we are using the AmpConnect 621 audio interface as we need at least 4 inputs – 2 are connected to the amplifier outputs and the other two to the HATS ears via the microphone preamps.

First the electrical loopback from the amplifier is used to measure the amp’s gain using the IEC weighted pink noise file, and this is used as calibration data for the subsequent measurements.

We then put headphones on the HATS and play noise while monitoring the signal through the ears on the multimeters to position the headphones for maximum output.

Next, we play IEC weighted pink noise at 50 mV while the signal from each ear is recorded, and a 1/3rd octave curve is analyzed. As before, A-weighting and free field corrections are applied and the values summed from 20 Hz to 20 kHz to indicate the overall weighted sound pressure level. 

Finally, the ratio between stimulus level and sound pressure level is used to calculate the stimulus level required to produce 94 dBSPL at the ears. This value, the wide band characteristic voltage or WBCV, must be greater than 75mV to comply with the standard.

So that’s how easy it is. You could of course program this from scratch yourself in SoundCheck, but the pre-written sequence will save you hours!