It is not an unusual thing where we as mixers have an issue with our mix translating in the theater. Of course there is very little that can be done if the theater is a badly calibrated one. But the issue I am talking about is where the projectionist turns the mix down because the amplifiers are clipping. So, the mix sounds soft. What happens next, is the mixes become louder. They turn down more. So much, that there can be no end to this. So as an audience if you feel you cant hear anything, don’t take word that the mix was like that. That might have been a very good mix turned down out of fear of the trailers or advertisements that come before and in the interval.

There is very little that can be done in this case. What I want to talk about is, as mixers what happens to the mix when it is turned down or what happens if you mix loud. How sure are you of your EQ and compression?

Pitch and Frequency

We all know that pitch and frequency are related. Did you know they are not directly related? Pitch is a very subjective term. This is also why some people have golden ears or are pitch perfect. Although pitch is derived out of frequency, it is very different from it. While frequency means cycles per second and is measureable and has the unit Hertz, Pitch is relative and uses a different unit called Mel.

Don’t fret if you haven’t heard of it. It is not so common. But hey, there is only so much technical stuff we want to read. So let me break it down as to why this is very important. It has been proved that a weak 1kHz signal is still 1kHz, but the pitch you hear is related to the level it is played back. In other words, 1000 mel is the perceived pitch of 1kHz at 40dB SPL. What can we infer from this? The simple fact is that if you have a 1kHz tone, and you increase or decrease level, the perceived pitch changes. Why is this so? Apparently it is related to the basilar membrane we have in our ears.

What’s interesting is that there are 280 steps of intensity and 1400 steps of pitch that the ear can technically detect. But in real world experiments, it was found that 7 levels of pitch and 7 degrees of loudness are what the ear can realistically detect. Ever wondered why there were only 7 notes in the music scale and why the Dolby Processor shows 7 as the standard playback level? (I am not too sure of the last one but I have seen that the decrease in levels of the processor is mapped very close to the decrease in response we have to the pitch.)

But why is this very important to us? Phonemes are the smallest unit in a language that separates one utterance from another. It is close to 49 (7pitch x 7 degrees of loudness). This is also how we can try and match performances in dialogue delivery using minor pitch correction on the stress syllables like the Ts, Ps, Es, etc. Very interesting! But that’s for another blog entry!

But now lets focus back to our mixes.

Perception and Levels

If you have a DAW, you can perform the following experiment quite easily. Make two mono tracks and assign one to the left and the other to the right. On each channel insert a signal processor and set it to sine wave. Set the left one to 168 Hz and the right to 318 Hz. Make sure your LR master is pulled down and the signal generator is at around -5 dB level. Here is the interesting part. At a low level, you will hear very discordant sounds. But as you increase the levels, you will notice that the pitch drops and you will get a pleasing feel of 150-300 Hz combination. Interesting isn’t it! The relationship for higher frequency is the inverse. Which means at higher levels, the pitch will increase.

The inference from this would then be that if you mix at higher levels and you start cutting frequencies or a pitch; that means you could actually be aiming for different ones. In this case the difference was around 20 Hz on each side. Imagine what happens in a real world situation. You would end up band compressing or EQ’ing different frequencies altogether. How critical is this? My experiences have been that at lower levels or EQ in isolation produces something that needs more modification when you have more elements added. So a guitar and voice at the same time would be a big pain. But then we can always perceive the dominant notes. If we do that, we next need to understand the lyrics.

This is also why if you play your mixes at a lower level, the lower frequencies rise in pitch and the higher frequencies fall in pitch thereby giving a very muddy mix that lacks clarity. But the added pain point? You will hear the distortions more clearly at a lower level.

Why so? The reason primarily lays in the way our ears function. Our auditory system has an inherent distortion. This has been experimentally proven by the presence of beats where close or first second and third harmonic produce a beat in the ears. The magnitude of the distortion lies in the level it is played back. Add to this where the ear will “Make up” a frequency from adjacent one assuming it is the fundamental (Ex: playing a tone of 1000, 1200, and 1400 will generate an aural frequency of 200 as the tones seem to be the 5^th 6^th and 7^th harmonic!). This also varies on the level being played. Again mixing loud will bring ghost frequencies that were never there in the first place!

So the question comes down to the fact that mix to what you think is a good level. Not too loud and not too low. If it is turned down in the theater, then it is obviously because its too loud. Of course the question is of the team of filmmakers understanding this. But then loud is not necessarily harsh, is it?

-FM