IEC 268-1 PDF

Sound system equipment – Part 1: General – SS-IEC Buy SS IEC Ed. 1 () Sound System Equipment – Part 1: General from SAI Global. Hi, I am reading a tech note named “The Loudspeaker Toster” by Pat Brown of Synergetic Audio Concepts and I would like to know what the.

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This new international standard recommends that for the measurement of audio-frequency noise in broadcasting and sound recording systems the weighting network have a response characteristic in accordance with curve Q in Fig. Wilms page mentions IEC1st ed. See the section below for a depiction of this curve.

For instance, in electrical connectors and standards for paper size A4 etc. The nature of the response in the top octave is especially important with magnetic coil input irc, since a resonance arises between the inductance of the coil and the load capacitance and resistance which causes a peak in the noise spectrum in the 10 – 20 kHz octave.

One must instead use a special “subjective audio noise meter,” usually known especially in Europe by the Greek word for noise meter, psophometer so’fameter. It seems there was an amendment to the original CCIR standard in to specify quasi-peak metering. I understand this stands for Broadcasting service for Sound. idc

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DIN was updated on While this standard was modified in some respects in later versions, andits weighting curve “Q” in the diagram below from Wilms has remained the same to the present day. I am not trying to document the Peak Programme Meter vs. The presence of a train of transients, each identical to the single transient postulated above, causes the averaging stage to charge to a value closer to the theoretical maximum.


The study evidently resulted in Dolby producing a weighting filter box and this being widely used by the company’s licensees.

The History of Low-Level Audio Background Noise Measurement

Thus the actual rise time of the 286-1 movement itself is not critical, since the peak value of the signal is “stretched”. I claim no copyright over these documents. Equivalent sound pressure level due to inherent noise uses CCIR weighting the “Q” curve in Wilms and quasi-peak metering. One step toward official acceptance has already been made. When the standard sound level meter became widely used, its A-weighting network began to be used iwc and more as a psophometric network, especially in English speaking countries.


This adjustment is for the difference between average and peak reading instruments; more about that later. The A weighting filter was rejected because it did not adequately represent the human sensitivity to higher jec noise, which appears in analogue tape hiss. Wilms gives the title for ASA S1.

An English translation of this important paper was kindly provided in February by Harvey A. As a result oec the stronger weighting of noise spectrum above 1. Since the numbers produced by the two systems will not be the same for any one noise signal, this would lead to further confusion for everyone.

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IEC Microphones Edition 4. Use of an RMS meter,which does not conform to the standard, produces 628-1 results which are about 4 dB lower, and therefore apparently better. As compared with the former weighting curve P 53 of the CCITT, there are differences in the measurement results because of the fact that the higher frequencies are now more emphasized.


This page only concerns low-level noise as perceived by humans. The most significant technical standards in this field are CCIR and its derivatives, involving quasi-peak detection of the filtered noise signal. A single pulse coming from a little scratch on a disc surface has a relatively low average level, but is not masked by the program in mezzo-forte passages. At white noise, the difference will be appr. This 2nd edition of replaces IEC and its three supplements: This web page will remain on the internet with this warning since other aspects of the design might be helpful to others.

It is well known that a measurement of the A-weighted sound level a so-called dBA reading gives a reading for impulsive sound sources which is too low compared with the real subjective results in phons determined by means of a listening panel.

A similar problem with the slowness of the “fast” rise time exists in the area of the sound level meters which follow the standards ANSI S1.

See quotes from Wilms below for more details.

This German technique of quasi-peak measurement has been applied in Germany and some other European countries since aboutalthough the first standard was not published until