Jason Downer
CopperCloudMusic
Sound Editor
Composer
Extra Ears Application Support Page
INTRODUCTION
Your ears are your best tools, trust them. This application is designed to help you ensure a good recording of dialog on a film set by being an extra set of ears.
Sets are noisy and sometimes chaotic. You can use this app to check for approaching airplanes, strange tones, room coloration, loud appliance noise, and on axis recording.
While it can use an internal microphone I recommend sending a mono headphone feed via a line in jack or externally powered USB interface.
Questions and comments about support issues may be emailed to ExtraEarsApp@gmail.com
FEATURES:
AIRCRAFT PREDICTION
This is the aircraft noise prediction display.
Information on the nearest aircraft to you is displayed above the prediction graph. When an aircraft is sufficiently close to ruin an audio take, this information will flash white and yellow.
The prediction display estimates the passing and combined noise level of the aircraft in your vicinity. The noise prediction is 3 1/2 minutes in the future.
There are three different markers for aircraft: Propeller Plane, Helicopter, and Jet Engine. Larger aircraft have larger icon sizes. Their relative altitude is represented vertically on the noise prediction display. While propeller planes and helicopters can be partially removed or softened in post production, as of this time, jet noise is nearly impossible to remove.
Loudness is shown in graph height as well as color. An aircraft's heading can vary, especially around take off and landing.
A gray color indicates a lower confidence in the noise prediction due to previous changes heading.
Darker greens are usually safe for indoor filming with closed or no windows.
Inaccuracies my also be caused by weather conditions which affect the attenuation and speed of sound as well as blocking due to terrain.
Only aircraft with an Automatic Dependent Surveillance-Broadcast (ADS-B) and Mode S transponder are shown. These technologies provide live, detailed aircraft information over the publicly accessible 1090 MHz radio frequency channel.
Data for this application is received over the internet from the OpenSky Network, a non-profit organization based in Switzerland.
There may be gaps in coverage in certain parts of the world due to a lack of volunteers.
FREQUENCY SPECTRA DISPLAY
For ease of use, Michaelis - Menten hyperbolic scaling is used instead of linear, log, or Mel scales. Guides are placed at 500Hz, and 1kHz through 17kHz in 1kHz increments.
Spectral information is displayed with automatic gain control and peak highlighting to enhance relative details rather than provide a consistent dB display.
A production sound mixer will hopefully be able to spot anomalies and problems easier with this type of display.
There is also a guide line at 100Hz or 120Hz depending on whether your GPS determined location uses 50Hz or 60Hz AC power, respectively.
Low frequency definition is increased via a Chirp-Z transform.
DBFS
dBFS, or Decibels relative to full scale shows a moving average of the volume the analyzer is receiving relative to a max signal for the mobile device.
LOUDNESS
dBA values are assumed to be an amplified signal through the internal mobile device microphone. This value is only a rough approximation due to variations of device model and microphone orientation. If using a line in, Bluetooth, or attached microphone this value is not reliable and should be used only as a relative guide.
AC HUM
Based on your location, the AC hum detector will automatically set itself for 50 Hz or 60 Hz.
Flashing red lines up to under 2kHz highlight harmonics of 50Hz/60Hz AC ground hum.
A Goertzel filter is used for sensing each harmonic.
HIGH FREQUENCY FLUORESCENT HUM
High frequency buzz that is notoriously difficult to remove in post production
REVERB DISPLAY and COMPOSITE RT60
In general, sounds with may reflections, reverb, or distance to from microphone exhibit a slow fall of signal.
CONSTANT TONES
This graph shows the tones or noise which are constant in the low volume portions of your signal. This can be from music, AC mains hum, air conditioning, aquarium pumps, or other appliances.
ON AXIS DISPLAY
In general, on axis and closely mick-ed voices exhibit rapid rise of signal and noise transients. The undulating green vertical line shows the sharpness of signal rise to judge microphone placement.
CLIPPING
Wireless microphones that are overwhelmed by sound levels will leave characteristic peaks in a voltage histogram, even if mixed with other sound sources. Microphone gain on the offending transmitter or line should be attenuated.
CLICK
Microphoes which are shorting or loose tape or rubbing hair can produce tiny clicks and disontinuties.
NOISE FLOOR
A running noise print is sampled and momentary signals are compared against it.
AVERAGE LOW VOLUME SPECTRA
This is a moving average noise print. Dark blue shows the quieter areas, while white and yellow show the places where there appears to be constant energy. This may be from hiss, appliances, or electromagnetic hum.
AVERAGE HIGH VOLUME SPECTRA
This is a moving average print of loud audio. Banding or dead spots can represent constant noise as well as sounds colored by early reflections off walls or if there are phase issues in your microphone feed.
AVERAGE VOLUME RISE RATE SPECTRA
Crisp signals that are recorded close to their sources will generally have fast rise times. A good on-axis recorded voice will show a straight green line. Sounds recorded more distantly will case a more wavy green line.
AVERAGE VOLUME FALL RATE SPECTRA
Sounds recorded without much reverb, echo, or room presence will had a straighter orange line, while distant, wet or ringing sounds will show a wavy orange line.