In a recent thread, I asked if anyone could recommend a simple way to measure HRFT. Rather than to try to correct for some average or modeled HRTF, I would like to have a more direct measure of my personal one. The plan was to then apply DSP to correct for it, in combination with headphones (and possibly speakers).
My initial thought was to try to run listening tests to determine the lowest dB level at which I can still hear each frequency in a frequency sweep. This sounds like it might actually produce a transfer function, combining headphone FR with my HRTF and also with my hearing acuity. A bit of work and possibly not very high degree of accuracy.
Meanwhile, I found a simpler and more direct way to measure HRTF that involves in-ear microphones. These microphones get inserted behind the pinnae in the ear so I can then use headphones over the ears to play a sweep to measure FR directly. I found in-ear microphones meant for binaural recording from Sound Professionals, part # SP-TFB-2. These are under $100, but if you don't have a recording interface that can provide 10-12v phantom power (48v will fry these!) you'll also need their battery power supply. They do sell an XLR version of these that work with 48v, but these cost more.
The mics are not calibrated, but their reported FR is pretty flat:
I found that the position of the microphone in the ear makes a difference to the measured response. Pushing it in as far as I could, I found the results fairly repeatable with +/- 1dB accuracy over the audible range.
Using REW log sweep into HE-560 headphones in combination with the binaural mics, here are the results for my ears:
This is different from the recommended Harman correction curve, which is not surprising as this represents a combination of HE-560 FR and my HRTF. Right is red, Left is blue. You can also see there are some differences between my left and right ears.
I then created parametric EQ settings to flatten the response (I'll spend more time in the future to fine-tune, but this was close enough for government work!) The corrected version, again measured with the same setup, is shown below. I didn't try to correct anything above 6KHz.
What does it sound like? Very, very nice! This is an obvious improvement over what I've been previously able to achieve with an average Harman HRTF correction curve, a simple flat curve, or a 10dB tilted one (20-20KHz). I have a few binaural recordings, and used those for testing.
Flat has never sounded good to me. Not over speakers, and not over headphones. Until now, the 10dB declining curve was my goto correction curve for both.
Interestingly, flat curve sounds great now, when it's measured from the inside of my ears! I also wonder if these measurements can be used to predict which headphone's natural FR would be a better match for my ears, if say I can't or don't want to do DSP. I'll have to subtract FR of HE-560s from the measured curve to determine my actual HRTF.
Comments?
My initial thought was to try to run listening tests to determine the lowest dB level at which I can still hear each frequency in a frequency sweep. This sounds like it might actually produce a transfer function, combining headphone FR with my HRTF and also with my hearing acuity. A bit of work and possibly not very high degree of accuracy.
Meanwhile, I found a simpler and more direct way to measure HRTF that involves in-ear microphones. These microphones get inserted behind the pinnae in the ear so I can then use headphones over the ears to play a sweep to measure FR directly. I found in-ear microphones meant for binaural recording from Sound Professionals, part # SP-TFB-2. These are under $100, but if you don't have a recording interface that can provide 10-12v phantom power (48v will fry these!) you'll also need their battery power supply. They do sell an XLR version of these that work with 48v, but these cost more.
The mics are not calibrated, but their reported FR is pretty flat:
I found that the position of the microphone in the ear makes a difference to the measured response. Pushing it in as far as I could, I found the results fairly repeatable with +/- 1dB accuracy over the audible range.
Using REW log sweep into HE-560 headphones in combination with the binaural mics, here are the results for my ears:
This is different from the recommended Harman correction curve, which is not surprising as this represents a combination of HE-560 FR and my HRTF. Right is red, Left is blue. You can also see there are some differences between my left and right ears.
I then created parametric EQ settings to flatten the response (I'll spend more time in the future to fine-tune, but this was close enough for government work!) The corrected version, again measured with the same setup, is shown below. I didn't try to correct anything above 6KHz.
What does it sound like? Very, very nice! This is an obvious improvement over what I've been previously able to achieve with an average Harman HRTF correction curve, a simple flat curve, or a 10dB tilted one (20-20KHz). I have a few binaural recordings, and used those for testing.
Flat has never sounded good to me. Not over speakers, and not over headphones. Until now, the 10dB declining curve was my goto correction curve for both.
Interestingly, flat curve sounds great now, when it's measured from the inside of my ears! I also wonder if these measurements can be used to predict which headphone's natural FR would be a better match for my ears, if say I can't or don't want to do DSP. I'll have to subtract FR of HE-560s from the measured curve to determine my actual HRTF.
Comments?
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