Loudness Measurement and Control

Sudden changes in loudness because of loud commercials and variations in loudness levels between programs have been a major source of nuisance for the consumers. With the transition to Digital TV, loudness related issues have not only continued but are on the rise. Traditional techniques of loudness measurement are ineffective for digital broadcast. Techniques for digital broadcast need to be objective and accurate. More importantly, these new loudness measurement techniques need to be mandated to control loudness for a consistent consumer experience. Governments around the world are realizing the need to regulate loudness to protect consumer interests. International organizations such as ITU, ATSC, and EBU have formulated recommendations specifying concrete thresholds and restrictions for loudness measurement. This paper discusses some traditional loudness measurement techniques and shortcomings associated with these techniques. The paper provides an overview of ITU BS.1770 loudness algorithm followed by basic requirements of CALM Act. The paper highlights the need for automated solutions that can meter the loudness and accordingly normalize the audio to ensure conformance to regulations. The paper concludes with a proposal for loudness control method that can be adopted in a file-based workflow.