Due to a discussion about whether or not listening to a movie in a THX theatre at reference level will damage your hearing or not, I'm trying to find info on the AVERAGE SPL of a typical action film, throughout the running time of the feature. Does anyone have any info on this? I know that music CD's are typically quite hard compressed nowadays and will average pretty close to -0 dB, but movies should be much lower - but how much?

I don't have that information, but I'm sure hearing damage is less likely to occur in a THX theater, simply because THX standard requires just about zero reverberation (if not zero) and flat response. (If this is incorrect please correct me).

I don't think I've ever walked out of a THX theater with a ringing in my ears despite that the sound is quite loud. Reference volume in a THX theater is tight and controlled, yet the same volume in a club (pretending it's the same sized room) puts your hearing out of commission for hours. This is because the latter is typically acoustically-treated very poorly and the same equipment isn't used. Now that I've seen how good a THX performance is (and how well it treats my ears) I can't see movies anywhere else.

I believe the average is 85 db, which over 2-2.5 hours is not going to cause permanent damage.

Here is a great paper by Ioan Allen from Dolby (warning PDF), which addresses the loudness of movies:
Are movies too loud? (www.dolby.com/assets/pdf/tech_library/54_Moviestooloud.pdf)

Enjoy... :D

The birth of Dolby 5.1
http://www.youtube.com/watch?v=0baFYLrPcWU

Ioan Allen "god damn it"
http://www.youtube.com/watch?v=k6r5ODqM6aY&feature=related

Dolby and THX spec that all channels be capable of average of 85 dB with peaks of up to 105 dB. The LFE channel must be capable of 95 dB average with 115 dB peaks.

Average SPL of a movie?

Depends upon how loud you listen. ;)

Depends upon how many loud scenes, full of effects, there are. ;)

Dolby and THX spec that all channels be capable of average of 85 dB with peaks of up to 105 dB. The LFE channel must be capable of 95 dB average with 115 dB peaks.

This is found not a realistic goal in home theater environment. Espicially true of smaller rooms with their own gain of the lower frequecies that are sent to the subwoofer. Your system should be capable of 105dB within +-2 of 0dB and play without distortion. Your room should be treated so that it is within the acceptable recommendations. On average the sound that has been mixed is not going to be 115dB peeks max and this is dependent of the studio. There is no home theater spec at this time.

While doing a little research on the proper average SPL for an HT system, I found this informative article, written by an Axiom Audio guru:

http://forum.ecoustics.com/bbs/messages/34579/341446.html

The article suggests that the best initial SPL setting for an HT system should average about 75 to 80 dB, allowing occasional peaks to about 85. There is a lot of other good stuff there, too. Read the whole thing.

I have found that the best sound level for my system for most movies and dramatic shows is pretty close to what the article recommends.

The article suggests that the best initial SPL setting for an HT system should average about 75 to 80 dB, allowing occasional peaks to about 85. There is a lot of other good stuff there, too. Read the whole thing.

I have found that the best sound level for my system for most movies and dramatic shows is pretty close to what the article recommends.

75 to 80 db should yield peaks close to 95 or 100 dbs..... I know in my system it does.

75 to 80 db should yield peaks close to 95 or 100 dbs..... I know in my system it does.
Like everything else, it depends on the source material. I watched Charlie's Angels today. I had recorded it from HBO HD and its peaks rarely exceeded 90 dB. Later, I watched Braveheart, which I had recorded from Showtime Hd. Braveheart did, indeed have louder peaks, sometimes approaching 100 dB.