Orban Introduces Free Loudness/Level Metering Software
Apr 11, 2008 11:32 AM
San Leandro, CA - Apr 10, 2008 - Orban has released the first public beta of Orban Loudness Meter software for Windows XP and Vista. It is available as a free download from www.orban.com/meter.
The company says that this is the first of a family of Orban meters. Future paid versions will offer upgraded features including logging, surround monitoring, and oversampled peak measurements that indicate the peak level of the audio after D/A conversion. This software simultaneously displays instantaneous peaks, VU, PPM, CBS Technology Center loudness, and ITU BS.1770 loudness. All meters include peak-hold functionality.
The software accepts two-channel stereo inputs. The VU and PPM meters are split to indicate the left and right channels. The PPM meter also displays the instantaneous peak values of the L and R digital samples. The CBS meter is a short-term loudness meter intended to display the details of moment-to-moment loudness with dynamics similar to a VU meter. It uses the Jones and Torick algorithm developed at the CBS Technology Center and published in 1981 in the SMPTE Journal. Created using Orban-developed modeling software, the DSP implementation typically matches the original analog meter within 0.5dB on sinewaves, tone bursts and noise.
The Jones and Torick algorithm improves upon the original loudness measurement algorithm developed by CBS researchers in the late 1960s. Its foundation is psychoacoustic studies done at CBS Laboratories over a two-year period by Torick and Benjamin Bauer. After surveying existing equal-loudness contour curves and finding them inapplicable to measuring the loudness of broadcasts, Torick and Bauer organized listening tests that resulted in a new set of equal-loudness curves based on octave-wide noise reproduced by calibrated loudspeakers in a semireverberant 16' x 14' x 8' room, which is representative of a room in which broadcasts are normally heard. In 1966, they published this work in the IEEE Transactions on Audio and Electroacoustics, along with results from other tests whose goal was to model the loudness integration time constants of human hearing.
In 2006, the ITU-R published Recommendation ITU-R BS.1770 Algorithms to measure audio programme loudness and true-peak audio level. Developed by G.A. Soulodre, the BS.1770 loudness meter uses a frequency-weighted RMS measurement intended to be integrated over several seconds - perhaps as long as an entire program segment. As such, it is considered a long-term loudness measurement because it does not take into account the loudness integration time constants of human hearing, as does the CBS meter.
Orban's BS.1770 loudness meter uses the Leq(RLB2) algorithm as specified in the Recommendation. This applies frequency weighting before the RMS integrator. The frequency weighting is a series connection of pre-filter and RLB weighting curves. The Orban meter precisely implements equations (1) and (2) in this document by using a rolling integrator whose integration time is user-adjustable from one to 10 seconds.
Additionally, the Orban meter offers an experimental long-term loudness indication derived by post-processing the CBS algorithm's output. This uses a relatively simple algorithm that attempts to mimic a skilled operator's mental integration of the peak swings of a meter with VU-like dynamics. The operator will concentrate most on the highest indications but will tend to ignore a single high peak that is atypical of the others.
Researchers have long been curious about the Jones and Torick meter but been unable to evaluate it and compare it with other meters. Orban developed this software because the company believed it would be useful to practicing sound engineers and researchers and also because Orban is using it in its new Optimod 8585 surround audio processor.
The Orban software runs on Windows XP and Vista computers having 1.5GHz or faster Intel Pentium 4 or Intel-compatible processors that implement the SSE2 instruction set. While the software can be driven by any installed Windows sound device, monitoring playback from an application such as Windows Media Player requires the sound hardware to support Windows Wave I/O.