Archive for the ‘microphones’ Category

How to Avoid “Cheap Movie” Dialog Audio Quality

Friday, December 14th, 2012

Web-research produced the following:

    or for (fully-formatted version):

    • The general rule, especially for beginners, is shotguns outside and hypercardioids inside. Lavs are okay when absolutely needed, though they often have a much drier, less natural sound to them because of where they’re placed. That missing ambience has to be added back in post. Wireless should be a last resort.
      • Unfortunately, a shotgun mic cannot be zoomed, and is not good at rejecting low-frequency sounds, including echos reflected from walls and floors.
      • Use of interference-tube shotguns are often the cause of that hollow, boxy sound you hear in low-budget indie films. Some shotguns, like the Sanken CS-3, use a different principle to achieve directionality, so are not susceptible to the same sorts of problems.
      • To get clean dialogue, the first and most important rule is to get the mic as close to the subject as possible. That means riding the frame-line with the mic and risking the occasional (hopefully rare ) dip into the frame. A lav mic on the subject can go a long way toward “solving” the problem of a reverberant room.
    • One of the biggest problems here is with small productions that have no sound person, and resign themselves to putting the mic wherever they can. On-camera is the absolute last place ever to place a mic for production sound. Get the mic off the camera and into the action. The effective working distance for a mic for on-camera dialog is 6″-20″, and 20″ is pushing it. The closer to the source, the more direct sound in proportion to ambient reflections will be recorded.
    • Audio that is recorded too low is going to have noise problems later. Not only will the levels have to be raised in post, increasing the level of any noise in the signal, low audio levels also create problems when audio plug-ins and filters are added. Since low (digital) audio levels don’t use but half, or less, of the available bits, processing through lots of things like compression and EQ can make the audio start to sound blocky (the sound equivalent of pixellated).
    • Room tone. Cutting dialog together requires some continuity of sound, and when taking a clip from take 1 and a piece from take 2 and cutting them together the room tone will be needed both to smooth out the edit (so that the room tone doesn’t disappear between lines) and often to keep continuity of sound between takes. If the traffic goes away, bugs start/stop chirping outside, or the room tone otherwise changes between takes, room tone is how you recover. Be sure to record :30 of room tone for each scene, and record it again if something changes. After the last take, ask everyone to stay still and quiet, and record in the same space with the same mics and with all the same equipment running.
    • Ambient sound beds add realism to the background. SFX and Foley replace all the sounds of people walking, moving, handling objects, etc. (none of that is actually recorded in production, where dialog is the only focus). Layers and layers of audio come together to paint the big picture.
    • The most common unidirectional microphone is a cardioid microphone, so named because the sensitivity pattern is heart-shaped.
    • A hyper-cardioid microphone is similar but with a tighter area of front sensitivity and a smaller lobe of rear sensitivity.
    • A super-cardioid microphone is similar to a hyper-cardioid, except there is more front pickup and less rear pickup.
    • These three patterns are commonly used as vocal or speech microphones, since they are good at rejecting sounds from other directions.
    • {This has a mine of information on microphone types, designs and properties in-situ indoors etc.}
    • A shotgun uses an interference tube that relys of phase interactions between that portion of the sound wave hitting it from the front, entering the tube through the front and traveling down inside the tube and the portion of the same wave passing alongside the tube and entering it through the side ports.
      • For sound coming from dead-ahead, the two wave sets in the tube reinforce each other but for sound hitting it from the side the waves are out of phase and cancel.
      • However, when considering sound reflected from the environment, its phase is already shifted with respect to the direct component of the same sound and so the pattern of orderly cancellation in the interference tube breaks down and some frequencies are reinforced while others cancel. The result is called ‘comb filtering’ and results in distortion of the recorded sound, typically sounding like the source is down in a well or standing in a metal culvert.
    • In comparison, hypercardiods do not use phase interference to achieve their directivity, operating instead on pressure differentials. As a result, they are not subject to the same degree of selective frequency distortion of the reflected sound that an interference tube mic exihbits.
    • Sanken CS3-e is a shotgun with 3 capsule array giving it better and more even frequency balance for the sides. Many have found that it is a shotgun which can be well used also indoors, it is also fairly compact in length.
    • {Discussion thread about recommended makes/models of hypercardiod mics}
    • Used ‘Mint’ Sanken CS3e microphone with Rycote Modular WS4 Kit
    • Price: £1,260.00
    • Sale price: £846.52+ Vat