85db pink noise, MUCH louder then 85db on DVD..

Discussion in 'Speakers' started by Mike_T_, Jan 16, 2004.

  1. Mike_T_

    Mike_T_ Stunt Coordinator

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    When calibrating my speakers to 85db with Avia with an SPL meter..the pink noise has to get VERY loud before it reaches 85db on the meter. However after I calibrate and watch a movie to test it out, I look at the SPL meter and see that during normal (somewhat quiet) scenes, the meter is at 85db (which from my understanding is correct for dialougue).

    So, why is the pink noise SO loud when you calibrate to 85db, but SO much more quiet for movies???
     
  2. Mike_T_

    Mike_T_ Stunt Coordinator

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    By the way, this stems from a recent paranoia I have that my system isn't performing up to it's highest level because of the way it's set up incorrectly, or calibrated incorrectly.. Anyone else feel this way? I think I've become obsessed with calibration, settings etc.
     
  3. Richard Burzynski

    Richard Burzynski Second Unit

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    Mike:

    I'm going from memory, but:

    * Avia DVD uses 85 db
    * Video Essentials DVD uses 75db
    * Receiver Pink Noise uses 75db

    Rich B.
     
  4. Mike_T_

    Mike_T_ Stunt Coordinator

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    I hope I'm not being confusing here... I was saying that when I pop in Avia to calibrate the speakers, I turn on Avia's pink noise and begin turning the volume up on the rotel until the meter shows 85db...and it's VERY loud.

    The same 85db on the meter during movies/music..is MUCH more quiet... why does Avia's pink noise sound so loud to get 85db compared to other sounds from movies/music?
     
  5. David Judah

    David Judah Screenwriter

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    Yes, Mike, I know what you mean. Sometimes when the whole family is watching a DVD, I'll hear something that doesn't sound right and I'll start adjusting things while everyone is watching the movie. It is a definite condition I call "tweakitis." Luckily, I'm not afflicted with it all of the time.[​IMG]

    DJ
     
  6. David Judah

    David Judah Screenwriter

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    Probably because the pink noise is constant and spread over a wide variety of frequencies, whereas the actual material is loud for a brief amount of time, followed by quieter passages and in a narrower range of frequencies at any particular moment(for the most part).

    DJ
     
  7. Brian L

    Brian L Cinematographer

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    Well, in my experience, after calibrating to 85 dB, if I then play a movie and adjust the volume knob to that reference, the sound is ridiculously loud.

    Even 10 to 15 dB (on the knob) below reference is relatively loud. Listening at calibrated reference in a typical den or living room is brutally loud.

    Me thinks something else is squirrelly here.

    BGL
     
  8. Chriss M

    Chriss M Second Unit

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    reference level is supposed to be loud. you should probably find -25 or -20 to be an reasonable listening level. remember, every 10db increase in spl is perceived as a doubling of volume. that makes reference level FOUR TIMES as loud -20.
     
  9. Jeff Gatie

    Jeff Gatie Lead Actor

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    Brian,

    Reference is extremely loud by definition (110 dB peaks for regular, 115 dB peaks for LFE). That's why many of us do not listen at reference level.

    To answer the question, the pink noise seems louder because it is a test tone encompassing all frequencies. The dialogue you are hearing is select frequencies and is understandable as dialogue. Rest assured if it measures 85dB, it is just as loud as the pink tones at 85dB. You just don't "hear" it as loud because it is not a constant random tone.
     
  10. Robert AG

    Robert AG Stunt Coordinator

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    The pink noise signal on the Avia disc is full bandwidth pink noise verses the band limited pink noise that is on other DVDs and what comes out of receivers and preamps. Since this signal contains all frequencies across the entire audio band, it will sound louder than the other test signals which are only producing engergy in the vicinity of 1Khz.

    That is the reason it sounds louder.
     
  11. Mike_T_

    Mike_T_ Stunt Coordinator

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    All of that makes perfect sense, however if it sounds louder to the human ear, why wouldn't the meter register this extra 'noise' on the meter as well? Decibel's are measurements of sound waves and human ears are also capable of measuring these waves. We all certainly know when something is loud or quiet. So, it just seems strange to me that speech during movies that registers 85db, sounds so much quieter then the intensely loud pink noise that Avia projects to reach the same meter level reading.

    If the pink noise covers all frequencies, you would assume it would have a greater impact on the meter reading, then just say someones voice which usually doens't reach too high, or too low on the hz scale.
     
  12. Lee Carbray

    Lee Carbray Second Unit

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    I got a BFD for Christmas, subseqently I have come down with a severe case of tweakitis.
     
  13. Mike_T_

    Mike_T_ Stunt Coordinator

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    I watched the Chiefs playoff game last weekend and they had a decibel meter there that was reading 102-103 which they said was of course, extremely loud. One of the announcers should have said "Those fans are damn lucky that's not pink noise!"

    It's like this..there are two men, one of them is 6'9" and weighs 350 lbs. (pink noise) The other man is 5'4" and weighs 120 lbs (regular speech on a DVD). They step on a scale and the 120 lb man gives the same reading as the 350 lb man. That's what's happening as far as I can see.

    The sound pressure meter is supposed to measure how loud something is. It's measureing something that to my ears is extremely loud, the same way it's measureing something that to my ears is relatively quiet. That's what I don't understand...
     
  14. Robert AG

    Robert AG Stunt Coordinator

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    Wideband pink noise does in fact have more "energy" in it than band lmited pink noise. It sounds louder for the same SPL reading because it contains frequencies that are in the ear's most sensitive region, and continues to the high frequencies - filtered pink noise from the other sources do not have these higher frequencies, only an approximately 1 octave band centered around 1Khz, falling off sharply on either side of this frequency. It is rather more benign to listen to.
     
  15. John Kotches

    John Kotches Cinematographer

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    Mike,

    First off, Pink noise is equal energy per octave....
    So there's the same amount of energy in the 20-40Hz as there is in the 10-20kHz region...

    To a certain extent, an SPL meter doesn't care about what frequency is out there. It's merely measuring the pressure of the wave, and displaying it as an SPL Level. Granted, the most common meter (a good old Rat Shack) has some variations in response vs. frequency, but that's not my point [​IMG]

    The catch is that movie soundtracks aren't pink noise (duh) and are perceived quite differently by our ears.


    Jeff Gatie:

    Almost correct on SPL levels, it is 105dB (peak) at the seats for main speakers (not 110) and 115dB for the LFE channel.

    All:

    THe difference between reference level in a movie theater and your own home is mostly due to the size of the room. 105dB in a huge theater is dramatically different than 105dB in your house [​IMG]

    Cheers,
     
  16. Robert AG

    Robert AG Stunt Coordinator

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    >>>The catch is that movie soundtracks aren't pink noise (duh) and are perceived quite differently by our ears.
     
  17. Mike_T_

    Mike_T_ Stunt Coordinator

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    Well it's clear I have no idea what I'm talking about :b

    Thanks for the discussion! I still have to experiment to see what I prefer. Calibrating using Rotel's pink noise or Avia's. They're both supposed to be calibrated to 85db..but I get different readings using both.
     
  18. Jeff Gatie

    Jeff Gatie Lead Actor

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    John, you are correct, I knew it was 105 and wrote 110, duh!
     
  19. Robert AG

    Robert AG Stunt Coordinator

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    The important thing is that whatever source you use, you balance all the speakers in relation to each other's SPL reading. This is way more important than the absolute level you calibrate to, or which signal you use. Most people don't listen at "reference" level anyway. The reference level is just the preferred mix level of the picture's director - and who knows, he/she just may be partially deaf to begin with!! Most that I work with are not audiophiles by a long shot.
     
  20. John Kotches

    John Kotches Cinematographer

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    Mike,

    The Rotel should calibrate to 75dB, as the tones are -30dB FS, whereas on AVIA, the tones are -20dB FS.

    FS in this context means Full Scale signal, which is 105dB. The 10dB pad for the LFE channel is corrected for on both AVIA and the Rotel.

    Cheers,
     

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