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Fletcher Munson Curve, Listening Volumes and Sound Perception

Discussion in 'Sound Science' started by baskingshark, Dec 17, 2019.
  1. baskingshark
    Hi, I'm not an audio expert but just a music lover, and I'm wondering about the Fletcher Munson curve and how this affects our perceptions of sound signature/FR with different listening volumes.

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    My interpretation of this curve is that as the SPL of music changes, the perceived loudness/energy of certain frequencies that our brains interpret will change. (Please correct me if I'm wrong).

    As we all have different listening volumes (for both lay consumers and reviewers), can we even be speaking on the same page when a reviewer is comparing or leaving impressions on an audio gear (like headphones or IEMs) when most reviewers or consumers don't even mention what is their listening volume at? Some like it loud, some listen very softly, not to mention we all use different sources, different ear tips, have different hearing health and different ear anatomies. To make matters worse, certain gear are very sensitive, like highly sensitive IEMs, and I'm pretty sure our interpretation of certain frequencies will be affected (not sure to what extent) with SPL.

    Thank you in advance for any input! I'm keen to learn more about this phenomenon, and if it is truly affecting our perception of music, we should all open with a disclaimer of each audio gear review with what volume we are listening to our gear at.
     
    SoundChoice likes this.
  2. bigshot
    My AVR has a dynamic loudness button that compensates for that automatically. I don't know why they don't put that on all amps.
     
    baskingshark likes this.
  3. castleofargh Contributor
    The subjective perception of loudness is as you see on the graph and it does change with the listening level. Your own hearing probably has some slight differences compared to those average curves(depending on your age, hearing damage, etc). Also we don't all have the acoustic reflex triggered at the same sound level, so that's got to have some impact too as I very much doubt that the mechanical action affects all frequencies equally.
    I think the most obvious and easy thing to notice at low level is the loss of low end. because even when we're not focused on it, going from some fair amount of rumble to whatever is left at low level, that's something we tend to notice.

    On the bright side, half of those worrisome curves don't concern you. Even while listening quietly, the music is still probably mostly above 40dB SPL, and 100dB is pretty loud. Those graphs can only be made in an anechoic chamber for a listener to even notice a tone at 0dB or lower. But yes our hearing is non linear in many ways so a listener's habit could impact his impressions. I wouldn't worry too much about that though, as there are many other reasons causing way bigger subjective variations between listeners. Those impressions are simply not very reliable in the first place, and I'm not even talking about the flaws of sighted impressions. Just our HRTF can make 2 people perceive the same headphone differently.
     
    baskingshark likes this.
  4. Roseval
    baskingshark and castleofargh like this.
  5. christianmc
    Doesn't matter for recreational listening. Comes more into play for mastering engineers and balance engineers.
     
    baskingshark likes this.
  6. baskingshark
    old tech likes this.
  7. gregorio
    Couple of problems with that: Firstly, it's a nearly 20 year old article and not entirely accurate today. Secondly, it accounts for room size by making 83dBSPL relative to -14dBFS, whereas theatrical film is 85dBSPL relative to -20dBFS. So at -20dBFS the relative SPL suggested would be 77dBSPL (or 97dBSPL at 0dBFS). That level is very loud but OK in a large living room, sitting say 4m from the speakers but would be too loud in a smaller room and/or closer to the speakers. Also bare in mind that it covers the entire spectrum (20Hz to 20kHz), whereas most consumer music systems do not and that would also result in a SPL setting than appropriate. A band limited (500Hz-2000Hz) pink noise test signal would alleviate this problem.

    G
     
  8. Roseval
    Thanks.
    That are the things I don't realize as a layman.
     

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