DK-Technologies MSD100C-Loudness Kullanıcı Kılavuzu - Sayfa 4

Müzik Ekipmanları DK-Technologies MSD100C-Loudness için çevrimiçi göz atın veya pdf Kullanıcı Kılavuzu indirin. DK-Technologies MSD100C-Loudness 10 sayfaları.

Sayfayı Yazdır

2.1

2.2

About the ITU BS.1770 Loudness Measurement

The ITU Recommendation BS.1770 specifies the algorithms to measure audio

programme loudness. The RLB-LU application implements these algorithms to

display the loudness of a Stereo signal as well as for a Surround Sound Signal.

(The MSD100C-LOUDNESS can only measure Loudness for a stereo signal)

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.

Applications

There are many applications, where it is necessary to measure and control the

perceived loudness of audio signals.

Examples of this includes television and radio broadcast applications, where the

nature and content of the programme 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 programme 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 the 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 the RLB-LU application

is based on an extension of the Leq(RLB) algorithm to cover stereo and

multichannel audio signals. In this algorithm 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.

Loudness is a perceptual property of an audio signal, when it is reproduced

acoustically. It is a complex non-linear function of amplitude, frequency and

bandwidth.

Present audio level meters measure the level of audio signals expressed as the

amplitude of the signal - either the rms voltage of an electrical signal or the

sound pressure of an acoustic signal.

This level is an objective property, which is independent of frequency and

bandwidth and is measured linearly in volts, if electrical, or Pascals, if acoustic.

For the purpose of broadcasting, loudness can also be measured as an

electrical property, assuming a fixed electro-acoustic gain for reproduction. This

assumption is the basis for the broadcast loudness meter. The reproduction

level, that has been assumed in the home, is 60 dBA. A level found to be typical

for television viewing at home.

The RLB-LU application has two main operating modes for different purposes:

Fast mode (SLIDE) for instantaneous monitoring of the loudness level. This

mode is used in production, post-production and presentation. The programme

level should be set so that on typical dialogue the meter displays 0 LU on

average.

Integrating mode for a single figure overall loudness. This mode is used for

quality control, mainly at programme ingestion, programme emission and in

post-mortem analysis. The single figure output from this mode allows clear and

unambiguous information for loudness matching and gain setting. This mode

makes it easy to secure consistent loudness over different programmes and

short sequences.