Proximity effect and the psychoacoustically wrong target FR curves

[thanrl]

Long time HF user here. Decided to start this discussion on ASR since afaik you are more welcoming to science-related discussions.

The proximity effect in audio is an increase in bass or low frequency response when a sound source is close to a microphone. When you speak closely into a microphone, your voice sounds more chesty. When you speak far into a microphone, your voice sounds more "normal". So far so good. Our eardrums also have proximity effects, because they function much like a microphone. When someone speaks to you at a distance, they sound like what they sound like. When someone speaks next to you with their lips almost touching your outer ears, they sound more chesty and intimate. Whispers sound especially different when heard close vs far.

Our brain is, unfortunately, adjusted to the proximity effect. When someone you know speaks to you at an extremely close distance, you expect them to sound more bassy. If you've only heard someone at an extremely close distance, you'd expect their "real voice", the voice if they were to speak to you at a normal distance, to be much less bassy than what you've heard, even if you've only heard their "close voice".

And this is why all IEM and headphone targets that intend to "mimic a 2-channel system in a room" are problematic. When we know the transducer is playing music next to our ears (because we have physical contact with the headphones), our brain expect the music to sound a certain way, a way that is different from what we know this music should sound in a good 2-channel system. We'd expect to not feel the bass through the body, but hear it in the ears; we'd expect every instrument to sound drastically closer. Having never heard the music in a 2-channel system likely won't help, because our brain is used to hearing things at different distances and perceiving them at said distance. Having never heard *any* music in a 2-channel system probably helps, or if one lived their life in hearing aids, but then we are talking about a different mindset of musical enjoyment entirely.

But why can't we just apply a known downward-sloping proximity effect FR on top of our existing headphone targets, problem solved? It is more complicated, actually. Every proximity effect I've mentioned so far is mono: a microphone picking up the sound of an instrument, a person whispering into *one of* your ears. The "stereo" proximity effect, by my estimation is a less steep downward-slope than mono. Imagine a person speaking in front of you. Now imagine a person speaking in front of the tip of your nose. They'd sound chestier, but less so than if they were speaking into only one of your ears. By how much? We don't know. In fact afaik there isn't a concept of "stereo proximity effect" in acoustic engineering.

Ok, then do a research on this topic and apply this "stereo proximity effect" on top of our existing headphone targets, problem solved? It is more complicated, again. Remember how the images of instruments are always "in your head" when listening to headphones? The distance of things in music reproduced by headphones are neither "in front of you, closer than the tip of your nose" nor "next to you, closer than touching your outer ears". The distance, far or near, is literally "in your head". I'd guess that our brain is initially quite confused by this too. So what does it say about the proximity effect? I don't know. Could be somewhere between the stereo proximity effect and the mono proximity effect. Could be something totally different.

The "tilted target FR curves" we are seeing these days are a great start. I hope in the future we can use tilt for specific frequencies and/or tilt with a curvature; that'll enable us to mimic proximity effect to a large degree. If you just want to enjoy a good sound, inductive science will certainly get you to where you need the target to be. Who is to say our brain will like a proximity-effect-adjust in-room target anyway? Once you hear it, you'll know it's right! But for the sake of a deductive science, a lot more work needs to be done to understand proximity effect of our eardrum and the psychoacoustics of perceived "distances."

 

[Galliardist]

Long time HF user here. Decided to start this discussion on ASR since afaik you are more welcoming to science-related discussions.

The proximity effect in audio is an increase in bass or low frequency response when a sound source is close to a microphone. When you speak closely into a microphone, your voice sounds more chesty. When you speak far into a microphone, your voice sounds more "normal". So far so good. Our eardrums also have proximity effects, because they function much like a microphone. When someone speaks to you at a distance, they sound like what they sound like. When someone speaks next to you with their lips almost touching your outer ears, they sound more chesty and intimate. Whispers sound especially different when heard close vs far.

View attachment 324389

Our brain is, unfortunately, adjusted to the proximity effect. When someone you know speaks to you at an extremely close distance, you expect them to sound more bassy. If you've only heard someone at an extremely close distance, you'd expect their "real voice", the voice if they were to speak to you at a normal distance, to be much less bassy than what you've heard, even if you've only heard their "close voice".

And this is why all IEM and headphone targets that intend to "mimic a 2-channel system in a room" are problematic. When we know the transducer is playing music next to our ears (because we have physical contact with the headphones), our brain expect the music to sound a certain way, a way that is different from what we know this music should sound in a good 2-channel system. We'd expect to not feel the bass through the body, but hear it in the ears; we'd expect every instrument to sound drastically closer. Having never heard the music in a 2-channel system likely won't help, because our brain is used to hearing things at different distances and perceiving them at said distance. Having never heard *any* music in a 2-channel system probably helps, or if one lived their life in hearing aids, but then we are talking about a different mindset of musical enjoyment entirely.

But why can't we just apply a known downward-sloping proximity effect FR on top of our existing headphone targets, problem solved? It is more complicated, actually. Every proximity effect I've mentioned so far is mono: a microphone picking up the sound of an instrument, a person whispering into *one of* your ears. The "stereo" proximity effect, by my estimation is a less steep downward-slope than mono. Imagine a person speaking in front of you. Now imagine a person speaking in front of the tip of your nose. They'd sound chestier, but less so than if they were speaking into only one of your ears. By how much? We don't know. In fact afaik there isn't a concept of "stereo proximity effect" in acoustic engineering.

Ok, then do a research on this topic and apply this "stereo proximity effect" on top of our existing headphone targets, problem solved? It is more complicated, again. Remember how the images of instruments are always "in your head" when listening to headphones? The distance of things in music reproduced by headphones are neither "in front of you, closer than the tip of your nose" nor "next to you, closer than touching your outer ears". The distance, far or near, is literally "in your head". I'd guess that our brain is initially quite confused by this too. So what does it say about the proximity effect? I don't know. Could be somewhere between the stereo proximity effect and the mono proximity effect. Could be something totally different.

The "tilted target FR curves" we are seeing these days are a great start. I hope in the future we can use tilt for specific frequencies and/or tilt with a curvature; that'll enable us to mimic proximity effect to a large degree. If you just want to enjoy a good sound, inductive science will certainly get you to where you need the target to be. Who is to say our brain will like a proximity-effect-adjust in-room target anyway? Once you hear it, you'll know it's right! But for the sake of a deductive science, a lot more work needs to be done to understand proximity effect of our eardrum and the psychoacoustics of perceived "distances."

I don't understand this claim. Surely, the established Harman curve for headphones (over ear, at least), preferred in controlled testing, is based on a "speakers in a room" response?

So what is "problematic" in that case? Don't you need more than an assertion to support this idea that the target is problematic and that there is even something to solve?

 

[fpitas]

IEM and headphone targets that intend to "mimic a 2-channel system in a room" are problematic

To my knowledge, the headphone targets are user preference curves, derived by testing. If they mimic in-room response of speakers that's only a reasonable outcome.

 

[thanrl]

I don't understand this claim. Surely, the established Harman curve for headphones (over ear, at least), preferred in controlled testing, is based on a "speakers in a room" response?

So what is "problematic" in that case? Don't you need more than an assertion to support this idea that the target is problematic and that there is even something to solve?

“we'd expect every instrument to sound drastically closer”, through a simulation of the proximity effect by the headphone FR. There, your TLDR

Afaik, some Harman research are done when the listener is presented with a speaker-in-a-room reference, some are not. It varies by the paper. I’m claiming that those that do are problematic.

To my knowledge, the headphone targets are user preference curves, derived by testing. If they mimic in-room response of speakers that's only a reasonable outcome.

That’s right. This post is not to criticize the Harman curve. This post is to theorize (one of) the contributing factor to the difference between the Harman curve (and other preference curves) and the DF curve (and preference curves derived by asking the listeners to use a speaker-in-a-room as reference). It is also to theorize the difference between preference targets among us: a warmer preference target is due to the person’s brain demanding more proximity effect, because a headphones that sound like speakers doesn’t “make sense” to it.

The goal is to start a discussion on the deductive science (where did DF target go wrong?), in the hope of meeting the inductive science eventually (after we correct what’s wrong with the DF target, do we arrive at the Harman target? Can proximity effect explain the difference between Harman target and IEF target?)

 

[IAtaman]

I am in no position the judge the accuracy of your idea, nevertheless, I appreciate it as an interesting perspective.

When we know the transducer is playing music next to our ears (because we have physical contact with the headphones), our brain expect the music to sound a certain way, a way that is different from what we know this music should sound in a good 2-channel system.

I think this is an assumption that can potentially be wrong. I don't think we can assume just because something is touching our ear physically,that our brain is going to interpret it as "distorted by proximity". A transducer next to my ears vs someone's lips next to my ears - they don't feel similar at all.

 

[thanrl]

I think this is an assumption that can potentially be wrong. I don't think we can assume just because something is touching our ear physically,that our brain is going to interpret it as "distorted by proximity". A transducer next to my ears vs someone's lips next to my ears - they don't feel similar at all.

Place your headphones on the table and play them at a loud volume. Now lower the volume and wear them on your head. If on the head they sound like what they sounded like from the table, you'd think your headphones are broken, no? Your brain expects a transducer to sound differently at different distances, much like everything else you hear. In fact, you'd know the headphones are now closer to you even if they aren't touching you and the volume is adjusted accordingly. Our brains are just that good at picking up positional cues.

 

[Deleted member 21219]

I think you are overlooking one factor. The music to which we listen holds ambient cues. Our brain latches on to those ambient cues and adjusts our "perspective" accordingly. If that were not so, then a "faraway" sound on a recording or in a movie would sound only as far away as our earphones. But that's not so. It's my opinion that the brain overcomes a great number of artificial restrictions to provide us with an expansive soundfield, and heroically ignores many barriers to doing so .... including close proximity.

Our brains are wonderful things, to be sure.

(If the music did NOT have these ambient cues included .... well, then I admit that all bets are off. It would be interesting to experiment and find out, though.)

Jim

 

[thanrl]

I think you are overlooking one factor. The music to which we listen holds ambient cues. Our brain latches on to those ambient cues and adjusts our "perspective" accordingly. If that were not so, then a "faraway" sound on a recording or in a movie would sound only as far away as our earphones. But that's not so. It's my opinion that the brain overcomes a great number of artificial restrictions to provide us with an expansive soundfield, and heroically ignores many barriers to doing so.

Our brains are wonderful things, to be sure.

(If the music did NOT have these ambient cues included .... well, then I admit that all bets are off. It would be interesting to experiment and find out, though.)

Jim

My point is that even the ambient cues sound differently when played at different distances. Would you agree? Therefore, to convey the same sense of ambient (e.g. as if you are in the concert hall), the FR of the ambient cues that are intended to playback in a living room will be different from those that are intended to playback next to your ears.

 

[Geert]

a warmer preference target is due to the person’s brain demanding more proximity effect, because a headphones that sound like speakers doesn’t “make sense” to it.

The brain does not need to make sense of the proximity of the on/in ear transducers, it just needs to listen to the music. Identifying the transducers technology is not the objective of wearing headphones or IEM's. You were them for convenience, and the fact that they're close to the ear is a side effect.

 

[DVDdoug]

IMO - Preference is the important thing since we listen to music for enjoyment. Your preference may be different from mine and the published curves are an average or consensus, but there's always EQ.

To me headphones or in-ears are simply a "different experience" and I usually prefer speakers. I'm not saying it's a worse experience... Some people like Coke and some people like Pepsi. (Excellent headphones are a lot more affordable than excellent speakers and you don't have to worry about room acoustics. I don't know as much about IEMs but I assume there are some affordable excellent ones.)

You are more likely to get a realistic "soundstage illusion" with speakers. Very few people get a good soundstage with headphones (me included) but that's not something affects my enjoyment of music one way or the other. Most of what I listen to is multi-tracked rock produced in the studio so the panning/soundstage is completely artificial anyway...

BTW - The microphone proximity effect is a side-effect of the way cardioid (directional) mics are designed mechanically-acoustically to kill/cancel soundwaves from the back. It doesn't happen with omnidirectional mics.

 

[Geert]

Place your headphones on the table and play them at a loud volume. Now lower the volume and wear them on your head. If on the head they sound like what they sounded like from the table, you'd think your headphones are broken, no? Your brain expects a transducer to sound differently at different distances, much like everything else you hear.

Again an error in reasoning, or a bad analogy. Headphones on the table don't sound crap because of your brains expectations. Measure them with a microphone at ear level and you'll notice the frequency response is hopeless.

 

[thanrl]

Again an error in reasoning, or a bad analogy. Headphones on the table don't sound crap because of your brains expectations. Measure them with a microphone at ear level and you'll notice the frequency response is hopeless.

The brain does not need to make sense of the proximity of the on/in ear transducers, it just needs to listen to the music. Identifying the transducers technology is not the objective of wearing headphones or IEM's. You were them for convenience, and the fact that they're close to the ear is a side effect.

Sir I think we are in complete agreement.

 

[thanrl]

BTW - The microphone proximity effect is a side-effect of the way cardioid (directional) mics are designed mechanically-acoustically to kill/cancel soundwaves from the back. It doesn't happen with omnidirectional mics.

Not claiming that our eardrums function like one particular mic or the other. Just that they exhibit *a* form of proximity effect.

 

[IAtaman]

Place your headphones on the table and play them at a loud volume. Now lower the volume and wear them on your head. If on the head they sound like what they sounded like from the table, you'd think your headphones are broken, no? Your brain expects a transducer to sound differently at different distances, much like everything else you hear. In fact, you'd know the headphones are now closer to you even if they aren't touching you and the volume is adjusted accordingly. Our brains are just that good at picking up positional cues.

Sure, it will sound differently but headphone's frequency response on the table, playing on its own will be very different to its FR on my head, and I don't think it is a function of proximity, I suspect it is probably a function acoustic impedance the transducers is facing.

 

[Deleted member 21219]

My point is that even the ambient cues sound different when played at different distances. Would you agree?

I have not found that to be true. However, 99% of my listening is classical orchestral music, and that might account for the difference in opinion.

Jim

 

[thanrl]

I have not found that to be true. However, 99% of my listening is classical orchestral music, and that might account for the difference in opinion.

Jim

May I suggest that it is because your wonderful headphones correctly adjust for the proximity effect in its tuning, and that you wouldn't have felt like you were in a concert hall if your headphones were tuned to the DF target?

 

[ReDFoX]

Place your headphones on the table and play them at a loud volume. Now lower the volume and wear them on your head. If on the head they sound like what they sounded like from the table, you'd think your headphones are broken, no? Your brain expects a transducer to sound differently at different distances, much like everything else you hear. In fact, you'd know the headphones are now closer to you even if they aren't touching you and the volume is adjusted accordingly. Our brains are just that good at picking up positional cues.

I guess it's more related to HRTF and nonlinearity of percieved loudness on different frequencies (equal-loudness contours), than proximity effect...

 

[thanrl]

I guess it's more related to HRTF and nonlinearity of percieved loudness on different frequencies (equal-loudness contours), than proximity effect...

They are definitely related, but neither of those can explain why you expect your headphone to sound different when placed on a table vs placed on your head, even when they are played at the same SPL measured at your eardrum.

 

[ReDFoX]

They are definitely related, but neither of those can explain why you expect your headphone to sound different when placed on a table vs placed on your head, even when they are played at the same SPL measured at your eardrum.

But... why? If we talking about "traditional" headphone design, in which drivers are parallel to our ears without any angling, it literally kills any spartial cues, since soundwaves fall into our ear canal under constant angle, which differs drastically from 60 degrees (for stereo), that we usually use for mixing and mastering music

 

[thanrl]

Sure, it will sound differently but headphone's frequency response on the table, playing on its own will be very different to its FR on my head, and I don't think it is a function of proximity, I suspect it is probably a function acoustic impedance the transducers is facing.

Or both! Try a different exercise, where the difference in volume wouldn't be as drastic so the impedance of the transducer isn't a concern: hold one of the earcups close to your ear but without creating a seal. Now hold it just a tad further while increasing the volume on the amp to match the perceived volume you hear. Does it get less bassy?