I am hoping somebody can help me with how I may perform the following test of Automatic Noise Reduction. First some details on the situation. I am a manager of a company that performs Avionics repairs, Prior to Covid I had a very knowledgeable staff that unfortunately required me to lay off staff members and we are currently trying to rebuild the team, The member I had that performed these tests and repairs is unfortunately not able to return due to illness and I need to figure out how he may have been able to perform these tests with the equipment we have.
The test equipment required is as follows:
1. Audio Test System (for purposes of this procedure the
Audio Precision System 2 is referenced) - We do not have this but have Audio analyzers HP 8903B
2. Artificial Mouth (Bruel & Kjaer 4227) - Have this model
3. Artificial Ear with 6cc Coupler (Bruel & Kjaer 4153) - Similar model
4. Supporting hardware for Microphone
5. Supporting hardware and software for audio test system
6. Custom ANR test and adjust fixture
Since we do not have the Audio Precision System 2 I do not know how the following test was performed and would like some help if somebody is willing to review the test.
Testing ANR
To test ANR, do the following:
1. Create a standard microphone test setup.
• Output should be 1V, 400Hz, BP Pink Pseudo noise directly out to
artificial mouth mounted to test fixture. See Figure 18
• Microphone amplifier filter should be set to A-weighing, if
available.
• Frequency sweep should be set to 500Hz–1KHz Bandpass input
filter.
2. Adjust headset to minimum size.
3. Place headset on test fixture. For more information, see Figure 18.
4. Measure the headset.
• With ANR turned off, perform a bandpass sweep, save this file.
• With ANR turned on, perform a bandpass sweep, save this file.
5. Subtract the two sweep results (files), measured in step 3.
The resulting curve should fit within the limits as shown in “Minimum
Attenuation Requirements (Linearize between points)”
Minimum Attenuation Requirements (Linearize between points)
Frequency (Hz) Active (dB)
Min Max
200 -8.000 +2.000
300 -1.000
400 -10.000 -2.000
600 -3.000
800 -12.000 -1.000
1000 -12.000 +0.000
We have everything except the Audio Precision System 2 and just cannot see how he was doing these tests unless he was just doing the math on paper using the audio analyzer, we also have spectrum analyzers as well but I don't think he was using that.
The test equipment required is as follows:
1. Audio Test System (for purposes of this procedure the
Audio Precision System 2 is referenced) - We do not have this but have Audio analyzers HP 8903B
2. Artificial Mouth (Bruel & Kjaer 4227) - Have this model
3. Artificial Ear with 6cc Coupler (Bruel & Kjaer 4153) - Similar model
4. Supporting hardware for Microphone
5. Supporting hardware and software for audio test system
6. Custom ANR test and adjust fixture
Since we do not have the Audio Precision System 2 I do not know how the following test was performed and would like some help if somebody is willing to review the test.
Testing ANR
To test ANR, do the following:
1. Create a standard microphone test setup.
• Output should be 1V, 400Hz, BP Pink Pseudo noise directly out to
artificial mouth mounted to test fixture. See Figure 18
• Microphone amplifier filter should be set to A-weighing, if
available.
• Frequency sweep should be set to 500Hz–1KHz Bandpass input
filter.
2. Adjust headset to minimum size.
3. Place headset on test fixture. For more information, see Figure 18.
4. Measure the headset.
• With ANR turned off, perform a bandpass sweep, save this file.
• With ANR turned on, perform a bandpass sweep, save this file.
5. Subtract the two sweep results (files), measured in step 3.
The resulting curve should fit within the limits as shown in “Minimum
Attenuation Requirements (Linearize between points)”
Minimum Attenuation Requirements (Linearize between points)
Frequency (Hz) Active (dB)
Min Max
200 -8.000 +2.000
300 -1.000
400 -10.000 -2.000
600 -3.000
800 -12.000 -1.000
1000 -12.000 +0.000
We have everything except the Audio Precision System 2 and just cannot see how he was doing these tests unless he was just doing the math on paper using the audio analyzer, we also have spectrum analyzers as well but I don't think he was using that.
Until you are able to hire someone who has an acoustical testing certificate employ a qualified (check the credentials) acoustical engineering co. Most likely you need to keep records for periodic inspection by a government body you don't want to mess with.
Stay with the people you hire to do the tests (field and office) and learn.
Sorry to be preachy! E
Stay with the people you hire to do the tests (field and office) and learn.
Sorry to be preachy! E
Hi Tunacan
I service AP's, program & design interfaces to provide full working test systems. Please call or Email me for greater details.
Best Regards
Duke Aguiar
1234 Coventry Dr.
Thousand Oaks, CA. 91360-5217
805-494-8171
Pacific Time Offset:UTC-7
LinkedIn
duke.aguiar@ieee.org
SOUND LOGIC LA ...
LinkedIn, Classic AP Audio Systems Group LA:
LinkedIn, Classic AP Audio Systems Group (Old group that can’t be updated)
I service and repair older AP Systems, write tests, procedures and develop ATE systems.
Your source for APIB USB ADAPTER for AP S1, S2, S2c & ATS2
I service AP's, program & design interfaces to provide full working test systems. Please call or Email me for greater details.
Best Regards
Duke Aguiar
1234 Coventry Dr.
Thousand Oaks, CA. 91360-5217
805-494-8171
Pacific Time Offset:UTC-7
duke.aguiar@ieee.org
SOUND LOGIC LA ...
LinkedIn, Classic AP Audio Systems Group LA:
LinkedIn, Classic AP Audio Systems Group (Old group that can’t be updated)
I service and repair older AP Systems, write tests, procedures and develop ATE systems.
Your source for APIB USB ADAPTER for AP S1, S2, S2c & ATS2
I have tested ANC systems in numerous headphones and I think I sort of understand your test setup. Doing that test with an HP8903 will be challenging due to it not having a tracking filter, just a tracking notch. You can use something like REW (free) with a PC + Soundcard to effectively measure the noise reduction of a headphone. If you have some specific standards you are measuring against it may take some adjusting to bring everything to match the standard. The artificial voice and artificial ear are the most specialized and expensive parts. You will also need a full range speaker and associated amplifier for the testing.
What I would do is first measure the open (no headphone) noise using pink noise or a swept response with REW. The mount the headphone and measure the noise reduction, first ANC off then ANC on.
I believe you are trying to validate function so comparing against known good headphones performance it what you want to do. The difference between the curve without the headphone and with the headphone will show the effective performance of the ANC.
PM me if you need more.
What I would do is first measure the open (no headphone) noise using pink noise or a swept response with REW. The mount the headphone and measure the noise reduction, first ANC off then ANC on.
I believe you are trying to validate function so comparing against known good headphones performance it what you want to do. The difference between the curve without the headphone and with the headphone will show the effective performance of the ANC.
PM me if you need more.