En50322 2 std

Transforming Sound into Knowledge

Sequence Note

EN50322-2 (Max SPL Standard)

Introduction
These two sequences follow the test standard detailed in EN50322-2 for measuring the maximum levels of
portable music players and earphones/headphones. This section of the standard covers the individual testing of
the devices rather than the combined testing that is detailed in -1. Note that the physical setup and connections
will be different between the two sequences. Please read the hardware and calibration sections of this instruction
carefully.
The sequence for testing the music player involves loading a weighted pink noise stimulus file (as specified by
IEC 268) onto the portable device and playing it through the headphone jack (connected to a 32 ohm load) at the
player’s maximum volume. The RMS voltage is averaged over 30 seconds, and the result must be less than 150
mV.

Final Display for EN50322-2 Headphones sequence

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-1-

The sequence for testing the headphones requires the device under test to be connected to an amplifier whose
output impedance is less than 2 ohms. The amplifier’s outputs are split, connecting one side to the headphone
and the other directly to the input of the soundcard. This is done to measure the voltage at the headphone while
the amplifier is under load. This also requires an audio interface with 4 inputs, as two will be connected to the
amplifier outputs and two will be connected to the HATS ears (via the microphone preamps).
The first part of the sequence uses the electrical loopback from the amplifier to measure the amp’s gain using the
IEC weighted pink noise file. This result is stored and applied as calibration data to the subsequent
measurements.
The headphones are positioned on a head and torso simulator (HATS). First, two signal generators play the
noise file while the signal is monitored through the ears on two multimeters. This allows the user to position the
headphones to produce maximum output.
Next, two signal generators play the IEC weighted pink noise file at a level of 50 mV while the signal from each
rd
ear is recorded, and a 1/3 octave curve is analyzed. An A weighting is applied to the curves, as well as a free
field correction for the HATS. The values between 20 Hz and 20 kHz are summed to indicate the overall
weighted sound pressure level. The ratio between stimulus level and sound pressure level is used to calculate
the stimulus level required to produce 94 dBSPL at the ears. The standard refers to this value as the wide band
characteristic voltage or WBCV. The WBCV for each headphone must be greater than 75 mV.

Software Requirements
 SoundCheck 11.1
 2004 - Post Processing
 2005 - RTA
 2009 – Statistics

Hardware Requirements
 Audio interface with minimum of 4 inputs (i.e. Lynx Two or RME Multiface/Fireface)
 Head and Torso Simulator (with Free Field correction curves)
 Microphone Power Supplies (SoundConnect or equivalent)
 4231 calibrator
 Amplifier (Output Impedance < 2 Ohms)

-2-

Setup & Calibration
Note: Run the sequences directly from their exported folder rather than importing them into SoundCheck.
Player Sequence
1. Load the file IEC 268_1 pink.mp3 or IEC 268_1 pink.wav onto your portable music player and set the
device to maximum volume.
2. Connect the outputs of the left and right side of the music player to inputs 1 and 2 on the soundcard.

Headphone Sequence
1. The first time you open the Headphones sequence you will see the channel relinking dialog. Click the
dropdown next to all four channels and choose Add to System Calibration. Then click OK.

2. Next you will be prompted whether to import calibrated devices associated with the new channels. Click
Yes.

-3-

3. Likely you will then be asked whether to overwrite the device ‘unity cal (Read-only) in.dat’. Click No to
All.

4. Last, the calibration editor will open so that you can assign hardware channels to the newly added signal
channels. Assign the Loopback channels to Inputs 3 and 4. Assign the EN50322 Amp channels to
Outputs 1 and 2.

5. Connect the HATS microphone outputs to the preamplifiers, and connect the preamplifier outputs to
inputs 1 and 2 on the soundcard.
6. Calibrate the HATS ears as per the instruction in the SoundCheck manual (using the Ear Sim L and R
signal channels).
7. Open the free field correction curves for your HATS into the memory list. Save the two curves into the
single file HATS FF Correction Curves.dat located in the sequence folder. Overwrite the existing file.
8. Connect outputs 1 and 2 of the soundcard to the inputs of the amplifier.
9. The outputs of the amplifier will be split, with one part going to the headphones and the other to inputs 3
and 4 on the soundcard.

You are ready to start the sequence.

-4-

System diagram

Setup diagram for the music player sequence

Setup diagram for the Headphones sequence
-5-

Sequence Logic – Player

Type Step Name # Out In
(Overall sequence)
Mes Start Stimulus 1
Acq Multimeter 2 Direct In 1
Lim Max Output Voltage 3
Dis EN50322-2 Player 4

Sequence Logic - Headphones

Type Step Name # Out In
(Overall sequence)
Rec Recall Stimulus File 1
// Creates a variable for post
Mes Initialize Stim Level 2 processing
Mes Calculate Amp Sensitivity 3
EN50332 Amp L Loopback L // Initial Acquisition to calibrate
Acq 2 gen and 2 Mult 4 EN50332 Amp R Loopback R the amplifier
Lim Amp Gain Check 5
jump on pass to # 7: Calculate Amp Gain
jump on fail to # 6: Level Check Failed
overwrite curves
Mes Level Check Failed 6
Pos Calculate Amp Gain 7
// Overwrites the amp sens in
Pos Apply Cal Sens 8 memory
Pos Apply Cal Sens 9
// Recalls HATS FF correction
Rec HATS Correction 10 curves
Mes Position the DUT 11
Mes Pause 12
EN50332 Amp L Ear Sim L // Position headphones for max
Acq 2 gen and 2 Mult 13 EN50332 Amp R Ear Sim R level
EN50332 Amp L
Acq 2 gen and 2 RTA 14 EN50332 Amp R Ear Sim L Ear Sim R
Pos Free field correction 15 // Applies HATS correction
Pos Free field correction 16
// Calculates the power sum
Pos LAEQ 17 between 20Hz-20kHz
Pos Divide Values 18
-6-

Pos Divide Values 19
Lim WBCV 20
EN50322-2 Headphone
Dis final display 21

-7-

En50322 2 std

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