Loudness Measurement in accordance with ITU Rec. BS.1770 and BS.1771
Fast mode for real time control of loudness
Integrating mode for loudness gain setting
Selectable digital and analog stereo inputs
Displays left and right channel loudness as well as the summed loudness
Numerical display of summed loudness
Scale in Loudness Units (LU)
Audio vector oscilloscope and phase correlation meter displays
Full VGA color display and VGA output for external display
The ITU Recommendation BS.1770 specifies the algorithms to measure audio program loudness. The MSD100C Stereo Loudness Meter implements these algorithms to display the loudness of the individual audio channels as well as the sum of the left and right signals.
Different working modes of the meter are selectable, including:
Fast mode for real time control of loudness.
Integrating mode for measuring the loudness of a recorded section or the complete recording.
Gated mode for viewing loudness of audio material with long pauses (e.g. golf matches).
Applications There are many applications, where it is necessary to measure and control the perceived loudness of audio signals. Examples of this include television and radio broadcast applications, where the nature and content of the program material changes frequently. In these applications the audio content can continually switch between music, speech, and sound effects. Such changes in the content of the program material can result in significant changes in subjective loudness.
Moreover, various forms of dynamic processing are frequently applied to the signals, which can have significant effect on the perceived loudness of the signal. The matter of subjective loudness is also of great importance to the music industry and in production of commercials, where dynamic range processing is commonly used to maximize the perceived loudness.
Loudness Measurements It is thus well recognized that loudness metering is required for broadcast applications. The algorithm recommended by ITU and implemented in MSD100C-Loudness is based on an extension of the Leq(RLB) algorithm to cover stereo and monophonic audio signals. In this the Leq is an unweighted mean-square measure, while the RLB involves a high-pass frequency weighting curve referred to as the Revised Low-frequency B-curve.
