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Temporary Threshold Shift (TTS)

Discussion in 'Acoustics' started by nelmr, Dec 29, 2010.

  1. nelmr

    nelmr Active Member

    Okay, so is this dangerous or not? From what I've read if this happens one should remember what caused it and avoid repeating it.

    Well, I have mild temporary threshold shift with small bit of ache in my right ear. This occurred after listening to my sub trying to play the loudest scene in the movie Inception (elevator/mountain facility explosions) - you see we are having some friends over to watch it this weekend and I wanted to make sure the VTF-15H can handle at the desired level and setting.

    At the listening position I was getting peaks of 103dBC (109dBZ). But I did spend some time closer to the sub while listening for distortion, port noise, or bottoming out (about 3-4 feet and closer to the wall). I was having peaks up to and perhaps above 110dBC in that location. I had the DIY mic about 2 feet from the sub and it was maxing out (it was calibrated with REW to only go 113.5dBC) I had the movie at -10dBFS. Most dialog was around 65dB.

    The overall SPL of the scene was averaging around 85dBC Slow at the listening location. But I repeated the scene over and over while taking measurements and adjusting some settings on the sub. I did this for perhaps an hour or so, with maybe 10-15 minutes near close to the sub.

    So I'm writing this to ask at what SPL, and for how long, does it take to have TTS? And more importantly how dangerous is it? I realize there are various degrees of TTS, but still I'm curious if any of it is safe.
     
  2. Towen7

    Towen7 Well-Known Member Staff Member Moderator

    OSHA require hearing protection if the SPL is in excess of 115 dbA (slow) and the exposure is greater than 15 mins. As exposure time increases the the permissible dbA decreases (30 mins = 110 dbA, 60 mins = 105 dbA, etc.) The exposure time is cumulative.
     
  3. Flint

    Flint "Do you know who I am?" Superstar

    A little ear ringing from time to time won't hurt you. If your ears are ringing after listen to something more than a few times a month, you are asking for trouble in the form of tinitus and permament hearing loss.
     
  4. Flint

    Flint "Do you know who I am?" Superstar

    By the way, my answer did not list specific SPLs for a reason. Everyone has different sensitivities to sound and one person might be able to handle a higher sustained SPL than another. OSHA guidelines are intended to protect darn and near everyone.
     
  5. Randy

    Randy Well-Known Member Famous

    I have found that extended exposure to high SPL's actually makes me a little dizzy as I have aged. It gives me a bit of vertigo (for lack of better terms) from time to time. That is why I have worn earplugs to the last couple of concerts I attended and I will have them again tomorrow night for the Trans siberian Orchestra show.

    We have 10th row floor seats and I am sure it is going to be plenty loud. My wife said I am a pussy, but I have been to close to a hundred concerts and between the car audio and other crap i have exposed myself to, I think I have done enough harm to myself.
     
  6. Alien

    Alien Active Member

    Your problem I don't think may have come from this single incident but rather the culmination of exposure during all of the recent testing you've been doing.
     
  7. Maximo

    Maximo Well-Known Member

    Short term, high exposure DB should be ok. My big question is why in the heck do you need it that load? Aside from that. I feel that all loud noise does some kind of damage. But luckily for you, because if the frequency range that you were exposed to you are/were less likely to incurr permenant hearing loss.

    The reason frequency has something to do with it has to do with the anatomy of the ear. The cilia that register 4000 hertz are at the biggest risk.

    I found this. This is a great site.

    http://scienceblogs.com/startswithabang ... r_that.php

    He say's he can't here above 13000 hz. I wonder if his speakers just won't play above that. I am totally gonna try this at home.

    Edit: Damn! Ok, I just dd a couple of people in my office and it made me dizzy listening to moderate levels of higher frequencies (14000 and above). So please be careful playing with this.
     
  8. Alien

    Alien Active Member


    Edit: Damn! Ok, I just dd a couple of people in my office and it made me dizzy listening to moderate levels of higher frequencies (14000 and above). So please be careful playing with this.[/quote]

    Were they warble tones?
     
  9. malsackj

    malsackj Well-Known Member

  10. PaulyT

    PaulyT Behind the Curtain Staff Member Administrator Moderator Superstar

    A number of us have those, I think. I have at least 2 pairs... They work pretty well at damping without distorting the frequency spectrum overly much (unlike just sticking your fingers in your ears ;)).
     
  11. Flint

    Flint "Do you know who I am?" Superstar

    I have several pair: some I keep with my drumset, some I keep in my car, some I keep in my PC bag, and some I keep in my luggage. They come in different dB attenuation levels, so I have different versions for different situations. When I play drums for fun I use the maximum reduction, for serious practicing or jamming I use the medium reduction, and for recording or live performances I use the minimum reduction so I can hear as much as possible. Same idea for going to shows, loud punk rock noise shows require more reduction than say a folk/pop band.
     
  12. Flint

    Flint "Do you know who I am?" Superstar

    I didn't mention the alternative hearing protection:

    search for "Ear Peace" and "Surefire Sonic Defenders"
     

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