1. Introduction:
Loudness is used to improve the perception of audio. It is also referred as Loudness compensation or Loudness equalization.
Human auditory response is sensitive to the sound pressure level . When audio is played at certain sound pressure level all the frequencies are not equally perceived at the same level. In order to equalize perception of audio at all frequencies different gains needs to be
applied at these frequencies. The amount of gain required to be applied is function of signal level.
2. Signal Flow Description:
Loudness CAO is designed to apply different gains at certain frequency bands. Amount of gain applied is based on
Volume level. Usually Gain is applied at low and high frequency bands. Usually more gain is applied at low volume levels.
Loudness CAO uses below audio objects
1. ToneControlExtended
2. LUT
1. ToneControlExtended
Loudness CAO uses ToneControlExtended AO to apply the gain in certain frequency bands.
3-band ToneControlExtended is used. “Freq”, “Gain” and “Q-factor” for each band of ToneControlExtended can
be tuned to get desired frequency response. Tuning parameter Filter type for each band can be shelving,
parametric
2. LUT
LUT is used to store the tuning parameters Freq, Gain and Q-factor of ToneContolExtended AO. Tuning
parameter for different volume level are stored in LUT table. There are 51 tuning sets, each tuning set is 3 band
Tone Control. The tuning set is selected based on ControlIn connected to LUT. ControlIn pin has to be driven by
volume control. ControlIn can take value from 0 to 100 corresponds to 0% or mute 100 corresponds to 100% or
full volume
Loudness CAO is designed for stereo input and output
3. Tuning Panel:
Please refer below SFD of Loudness CAO.In SFD TonecontrolExtended is named as “Loudness3Bands_1_0_1”
