Lecture 2 (Summer) - Mix Judgements Flashcards
What are the most important mix decisions we will make based on?
Loudness judgement. Usually we use dialogue as the reference.
What is our dialogue reference level?
-18dBFS.
Between 4 and 5 PPM with occasional peaks at 6.
What is the minimum audible change that we can hear?
In the region of 1dB, but it depends on the source/listening conditions. In many cases, we wouldn’t detect a 1dB change in level at all.
There are situations where small changes in dB (especially frequency dependent changes) are noticeable so it is wise to listen, rather than simply look at the figures.
What tool do we use to change the gain of certain frequency bands?
EQ plug-in - different dials modify different parts of the frequency content.
Choose frequency, choose gain and choose the Q settings (bandwidth).
What difference in dB makes a source sound twice as loud?
It actually depends on various factors:
• Overall level
• Duration of exposure
• Monaural/binaural listening
• Spectral complexity/simplicity of sound source
In general, most people agree that ‘twice as loud’ translates to an increase of somewhat between 5 and 10dB
Hearing is not equally sensitive for all frequencies…
Loudness is frequency dependant.
We perceive lower frequencies as quieter, so to perceive them as the same level as higher frequencies we need to boost them.
What are Fletcher-Munson Curves?
- ‘Equal loudness countours’ (Fletcher-Munson Isophon Curves), they show different overall loudness levels with respect to frequency.
- Each Equal Loudness contour is called a Phon curve.
- In general, the number of Phons equals the number of dB at 1kHz, for a given chosen loudness.
- 1kHz is an arbitrary reference point with which to compare the loudness of other tones.
What are the two main results from Fletcher-Munson Curves?
- We have varying sensitivity for simple sine waves as we change the frequency.
- This sensitivity changes with loudness. Generally, at high listening levels there are less differences in our sensitivity over the full spectrum than at low listening levels.
At low levels, what can we do to ensure the high and low-frequency content can be heard? What problems can this bring?
Boost the high and low-frequency content. This can cause problems when the viewer may turn up the volume and they will sound too high.
We need to ensure that when we mix we are mixing at the appropriate playback level.
What level are cinema’s and mix rooms calibrated at?
85dB at the sweet spot (using pink noise).
What happens if we were to mix too quiet…say at 65dB?
• We would have even less sensitivity to bass, so we would overcompensate…
• What is the result when the mix is played back in the cinema?
Too much bass!
What is Amplifier ‘loudness’ control?
At low listening levels we may hear mid range information only, due to the relative insensitivity of the ear to low and high frequencies at lower loudness levels.
• For this reason a ‘Loudness’ switch is often incorporated on audio amplifiers which boosts low and high frequencies.
Is this loudness/frequency dependency taken into consideration in decibel measurements?
Yes! A standard decibel meter has settings that attempt to reflect the way the human auditory system works.
What is the SPL weighting for decibel meters?
A weighting - low listening levels <60dB (dBa) reflects our hearing more accurately.
B weighting - mid listening levels
60 - 80dB
C weighting - high listening levels >80dB (usually used for cinema …dBc)
A & C most common
What is a 5.1 surround sound system?
Has to do with number of channels,
5 - full range channels (playback all frequency content)
1 - low-frequency channel (sub-buffer, it’s an LFE - low-frequency effects - channel). This is so that we can boost the low-frequency level without affecting the rest of the frequency content.
