Sound levels

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Peter Copestake
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Sound levels

Post by Peter Copestake » Wed Jan 22, 2014 6:42 pm

How do you ensure that anyone playing your discs doesn't have to adjust the volume after they start watching?
One way that I can think of would be to ape the old films and have a lion's roar or a large gong that was the loudest part of the whole film but that seems a bit over the top for a modest amateur film which you may want to start quietly. Alternatively I suppose we should all be able to set the volume so anyone can play it on their equipment without needing to change levels.
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col lamb
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Re: Sound levels

Post by col lamb » Thu Jan 23, 2014 5:27 pm

By having a leader with the sound level set at your desired value relative to the content.

Ie a 10s leader (PC Productions logo etc), then movie, the watcher will then set their desired listening volume during the leader
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Dave Watterson
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Re: Sound levels

Post by Dave Watterson » Thu Jan 23, 2014 8:33 pm

I think Col is assuming the leader will have a sound tone on it!

There used to be standards used by Hollywood, but in recent years film producers, keen to enhance their blockbusters have gone for higher and higher volumes. Anyone attending a modern commercial cinema can testify to that. Ironically cinema managements fearing complaints and possible claims for damage to ears have taken to turning down the volumes.

The BBC requires that the leader have the EBU 1kHz tone - read the rest of the BBC standard here (page 10 for sound): http://www.bbc.co.uk/guidelines/.../Tec ... BBCv2.pdf‎ OR Google "bbc technical standards" and the link is usually the second on the list.

Then you have to ensure your soundtrack conforms to the standards set by that leader ...

For practical purposes I suggest you make sure the leader contains a tone that plays at around the general volume your soundtrack will use. On the disc ask the projectionist to set levels to suit that tone.

Peter Copestake
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Re: Sound levels

Post by Peter Copestake » Fri Jan 24, 2014 5:50 pm

Thanks, both Colin and Dave.
I couldn't get the link to the BBC to work, Dave, but the BBC is not that good at getting sound levels right in my viewing experience.
I used to have a 5 note jingle to go with 'Pendle Life Time Films' when I was using cine but I haven't used it for video and it's too short to adjust volume, probably, but I'm sure you're on the right track, Colin, as the professional sustained tone is not suitable for home-watched DVDs or someone else showing to a small audience, I feel, Dave.
My only concern with Colin's suggestion is that it seems a bit much for a simple film and if used several times in a show would get boring to the audience.
I think I must standardise my productions better first. Max -6dB on the edit programme's mixer control?
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Roy1
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Re: Sound levels

Post by Roy1 » Sat Jan 25, 2014 9:55 am

Peter. I appreciate what you are wanting to do but is it that important. If I receive a number of videos to be shown in public I play them through in private and make a note of the volume level required and when the show is on I alter (if required) the volume level before the video plays. The volume bar shows only on my monitor and not on the public screen. As regards to the video being played by an individual person on a TV, it has to be remembered that prople have different levels of hearing and the individual has to adjust the volume to suit his hearing levels. But I think you do right to select a happy medium in the sound volume of your productions.

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Re: Sound levels

Post by col lamb » Sat Jan 25, 2014 1:07 pm

Peter
A sustained tone is only suitable in an offine studio to set the volume before transmission begins, otherwise in our situation it will result in th volume being turned down as its very annoying.

You are not limited to only using one opening logo sequence, make a number of them, save each as an avi or mpeg file and add different music to them for each movie such that the music is complimentary and just below what will be the mean sound level of the movie
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John Roberts
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Re: Sound levels

Post by John Roberts » Sat Jan 25, 2014 2:15 pm

Hi Peter,

Unfortunately setting the maximum level on the editing software is only part of the solution - apparent loudness is better defined in terms of RMS or average level, as opposed to peak, or maximum levels, but it's also about controlling the dynamic range of the film.

The range of audio level between loudest and quietest sound is called the dynamic range, and I would aim for a maximum dynamic range of about 30dB or so across the majority of the production. Your quietest sounds should therefore be about 30dB quieter than your loudest sound. Much below this, quiet sounds have a tendency to disappear in the ambience of the room or hall where the film is being shown, especially if the amplifier volume is set low. Most sounds, including ambience, dialogue and music should fall within a 20dB range.

When looking at a typical editor's peak audio level meter it's often difficult to interpret what the RMS or average sound level is. If you don't have access to a PPM meter plug-in, then take a look at what the meter is doing, in particular where the bulk of the sound seems to be (the rough area where the lights form a solid block) which we can take to be an approximate RMS guideline. A louder soundtrack will have it's RMS level (the solid block) higher up the meter, regardless of peak level. The RMS level really depends on the audio content on the timeline and this is the hardest to get right. The BBC broadcast guidelines suggest most sounds should fall within 20dB of maximum, which will give you another 10dB under this in order to accommodate quiet ambience. Remember the analogue VU meters we used to have on tape/cassette decks? If they didn't move it was too quiet, if they went into the red it was too loud. They had a little over 20dB range between too quiet and too loud...

Audio clips may need the use of a limiter or compressor to control peaks if the clips are too dynamic. One film I recently judged had a very well balanced soundtrack, but the overall volume was far too low. On investigation I found the film soundtrack had a peak value of 0dB, but an RMS value of -30dB, with quiet sections approaching -50dB. The problem was caused by two very short sounds - one was a door slamming, the other something being dropped - that peaked at 0dB. The film producer had turned the master volume down to avoid exceeding 0dB and creating distortion, but the entire films soundtrack had also been turned down with it. Using a compressor set up to affect only the two errant sounds would have controlled the excessive peaks and allowed the producer to keep the soundtrack at a higher volume. Peaky sounds that aren't obvious can be identified by simply muting certain audio tracks or clips at the point on the timeline where the peaks occur - when the peaks are suppressed, you've usually found the sound.


However, once the dynamic range is more or less sorted and the soundscape sounds well balanced to your ears, we then need to decide what the overall volume of the soundtrack should be. And herein lies the problem because outside of broadcast standards we can pretty much do what we want. Current BBC standards set a reference point of -18dB (in simple terms we can say most sounds average around this level) with peaks NEVER exceeding -10dB. Following these guidelines the overall volume level of the soundscape you have just created should be adjusted so that the 30dB dynamic range appears between a maximum -10dB and -40dB. However, there's nothing stopping you from setting the maximum peak level to 0dB as many do. This is totally unacceptable as regards broadcast standard but completely acceptable and allowable by any computer based editor. What then happens is that when your 'correct' -10dB film follows an 'incorrect' 0dB film, yours appears at half the volume and the amplifier is turned up, hopefully. Or if the films appear in the reverse order, the amplifier's volume control is rapidly cranked down when the 0dB film blasts through the speakers at twice the volume of yours.

I have no idea how we can stop this happening, because no-one is 'policing' or enforcing any particular standard, and it could be quite difficult to do so. Adding a complex technical hurdle doesn't exactly attract newcomers to our amateur film-making world! It would be easier to follow broadcast standards in terms of dynamic range, but with a maximum allowable peak of 0dB, or just below the 'clip' light illuminating in the software. Then everyone will know what the maximum level should be and mix the soundtrack to within 30dB under this. Films made to broadcast standard (-10dB) can have an alternative version made with the output level increased to 0dB, likewise films made to 0dB maximum can be reduced by 10dB to fall within broadcast standards, as long as the dynamic range is controlled and within the guidelines. Or maybe DVDs could be marked up '-10dB' or '0dB' standard, in much the same way as they are marked with 4:3 or 16:9, then the projectionist/sound person will know exactly what sound level to expect...

I hope this helps, but I must admit I am not an expert on broadcast standard sound.

John

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Re: Sound levels

Post by Peter Copestake » Sat Jan 25, 2014 4:48 pm

I found John Roberts advice very thorough and he says he's not an expert! All relative, I suppose. Thank you, John.
I'd like to see that printed in FVM unless, of course, someone else can do it better. I'll certainly take a copy to "My Room"!
Colin, you are right of course. I am slow at thinking outside the box or whatever the expression is. Thank you.
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col lamb
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Re: Sound levels

Post by col lamb » Sat Jan 25, 2014 5:25 pm

Great post by John.

It is worth adding that in using the dB scale is not linear, it is logarithmic.
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John Roberts
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Re: Sound levels

Post by John Roberts » Sat Jan 25, 2014 6:14 pm

Yes this is true, the decibel scale is logarithmic. Thanks for that Col :)

If we only remember one thing about decibels it should be that each 10dB increase or decrease in level represents a doubling or halving of the volume. Therefore reducing the volume by 10dB halves it, reducing it by a further 10dB (20dB in total) halves it again, therefore it is four times quieter than it originally was. A further 10dB reduction (30db in total) halves it yet again so the sound is eight times quieter, and so on. That's one reason to avoid a vast dynamic range in our films - a 50dB range contains some sounds thirty-two times quieter than others, and these quiet sounds are simply lost in almost any environment other than hushed night-time home viewing or headphones.

Keeping the dynamic range of most sounds within 20dB or so gives a workable dynamic range but also ensures that once the sound level of a particular film is adjusted correctly during a show, everything within that film should be audible. It still doesn't solve the problem of where that 20dB range should be (technically it could be anywhere and it would still sound the same, only at a different volume level) and this is possibly something that needs to be addressed. Sound has never had the same degree of control placed upon it that perhaps it needs now, in this digital age where simple VU meters with their 'average' metering that kept everything in check, are rarely seen.

Maybe the IAC should consider drawing up some guidelines on this issue? We have constraints over pictures - format, aspect ratio, leaders etc - yet absolutely nothing about sound. Just a thought :D

John

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Dave Watterson
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Re: Sound levels

Post by Dave Watterson » Sat Jan 25, 2014 6:41 pm

John - have you any experience of using software sound meters?

http://www.darkwooddesigns.co.uk/pc2/meters.html has been in the IAC website's toolbox for a long time.

I ask because so few people have a stand-alone ppm meter or one built-in to their system.

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Re: Sound levels

Post by John Roberts » Sat Jan 25, 2014 8:17 pm

Getting there, Dave! My background is in music, having run a studio for over 30 years - and although the basics are the same there are subtle differences between using meters and mixing for music and doing so for films. Having drifted back into film-making I was amazed at the variance of sound between films shown back-to-back so I'm looking into metering and the standards more. In fact I'm just about to install a demo version of PSP's PPM and VU meters into MS12 to take a look. I've already installed them into MS11 on the laptop and tried using the PPM meter alongside the program's peak meter, with encouraging results. I'm going to check out the link you posted, especially if it's free, although the PSP full version is under a tenner.

I think the issue here is that even when the soundscape is correctly balanced, I've noticed films fall into two categories: those produced to 'broadcast standard' and those that aren't. The variations between those that 'aren't' are much greater than they used to be because of the metering of most computer editors - peak level meters are really only useful for ensuring the peaks of the audio don't exceed whatever level you desire, be it 0dB or -10dB. Other than that they're pretty useless at telling us how loud the soundtrack is. There is also very little point in having a peak meter that reads down to -90dB or even lower, unless one is checking where the 'noise floor' is. A meter with an extended scale can also be deceiving because the soundtrack looks loud when in fact it probably isn't. PPM meters are the best compromise but should be used in conjunction with a peak level meter, which will indicate transients too fast for the PPM to react to and ensure clipping doesn't occur or the soundtrack's peaks stay below -10dB if producing for broadcast.

But even when we've got that right, as amateur film-makers we still have no standard to adhere to. The broadcast standard is confusing for anyone not familiar with it because it doesn't use 0dB (the maximum allowable signal level through a typical computer based editor, and one we would assume is what we should aim for) as its absolute maximum level. And even if the majority of seasoned film-makers present their films at -10dB, there will always be a large number who don't, simply because they've probably never heard of the standard, don't understand it or don't want to implement it. So we're back to square one with Peter's question! :D

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Dave Watterson
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Re: Sound levels

Post by Dave Watterson » Sun Jan 26, 2014 12:06 pm

John ... why don't you write a standard to recommend to us non-commercial/amateur film makers?

You understand the broad aspects of sound and you are a fine movie maker. There are other members who have worked in television sound, in music recording and probably in the sound side of the film industry. But you have freshness, relative youth and infectious enthusiasm.

If you take it on, I suggest you keep it simple. For many film makers sound is an unknown country ... they just choose some music, speak some commentary and add it to the timeline. I mean, recommend x as peak level, y as acceptable range from lowest to peak and so on. By all means, mention that there are other standards and that other people may disagree ... but tell people "These will work."

No one can compel other film makers to adopt any standards. (We still have members working in 9.5mm.) But we are practical people. Given a sensible set of understandable guidelines, most of us will adopt them. That will be of benefit to all.

Of course you are busy ... but if you would give it a go, you could pop drafts on here and receive comments from other forum users - some of whom are those with expertise in recording. In other words, we'd help.

I would not get into all the aesthetics of building soundtracks. That is another and much more controversial area. This would be about basics.

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Re: Sound levels

Post by Peter Copestake » Sun Jan 26, 2014 3:53 pm

This all goes to show that there is much more to the IAC than many of us realise. Though a long-time supporter I had no idea about any of this especially the meters Dave says have been 'in the ... tool-box' for a long time.
Didn't know there was one! I now I've seen it I'm struggling to work out which one to try. Anyone with a simple aged brain like mine please advise. Seems I've hit on a subject that interests the forum for a change.
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John Roberts
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Re: Sound levels

Post by John Roberts » Sun Jan 26, 2014 4:31 pm

Hi Peter, I have a feeling this topic will grow and grow simply because there are a great many film-makers out there that are experiencing problems with sound - you're by no means the only one! :)

I did download one of the meters but for some reason it wouldn't initialise (I believe it was telling me it couldn't access the soundcard because something else already had - that would be my editing software, I assume) - so I need to try a couple of the others at some point. The PSP model I downloaded works well, but it's a VST plug-in (which works fine within Vegas) as opposed to a standalone meter.

As regards a standard to recommend, Dave, sure I can have a think about that. The BBC guidelines are pretty good but need translating into something that we can all understand and use. My only issue is their current use of -10dB as an absolute maximum peak limit, for the simple reason that there will always be film-makers who work to 0dB. I confess I now do, solely on the grounds that a number of 0dB films being presented at clubs and competitions used to make my soundtracks seem quiet, and if the projectionist/sound person isn't 'on the ball' the volume never gets adjusted and all my subtleties in the soundtrack are lost.

From a personal point of view, at my particular moment of research, I would like to see a 'BBC broadcast guideline' dynamic range, but with a maximum peak level of 0dB as a proposed 'standard'. Films made to broadcast specification will adhere to the same dynamic range, but be at -10dB so either the discs are marked '-10dB' or 'broadcast standard sound' in order to help the projectionist, or a dedicated version with the output level simply raised can be sent for competition use. As I mentioned previously, the dynamic range will still be the same, it's just where it 'sits' on the output scale; either 0dB or -10dB.

Only the broadcast professionals can collectively change their standard so there's little we can do about it. Some film-makers will only want to send in a broadcast standard soundtrack and they should be encouraged to do so. Some film-makers will work to 0dB because it's a natural thing to do, and they should not be discouraged from entering films. It's how we accommodate everyone that is the key.

Any sound/broadcast ex-professionals like to comment or add to this? I'm sure we can work this out between us all :)

John

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