Masking sound

Masking process by which threshold of audibility of one sound is raised by the presence of another (masking) sound. 

A peak sound pressure of above 200 pascals or about 120dB is considered unacceptable and 130dB is the threshold of pain for humans. If a person has to shout to be understood at 2 metres, the background noise is about 85 dB. If the distance is oniy 1 metre, the noise level is about 90dB. Continuous noise at work causes deafness, makes people Irritable, affects concentration, causes fatigue and accident proneness, and may mask sounds which need to be heard in order to work efficientiy and safely. 

As with troubleshooting, parameter estimation is not an exact science. The facade of statistical and mathematical routines coupled with sophisticated simulation models masks the underlying uncertainties in the measurements and the models. It must be understood that the resultant parameter values embody all of the uncertainties in the measurements, underlying database, and the model. The impact of these uncertainties can be minimized by exercising sound engineering judgment founded upon a famiharity with unit operation and engineering fundamentals. 

It is important to quantify the sound pressure levels in dB generated by each source and for each frequency (31.5-8000 Hz) in order to establish which noise will be masked or prevalent. It must be noted that when the pressure levels of two noises differ by more than 10 dB, the resulting level is equal to that of the higher-level source in other words, the noise at the higher level masks the noise at the lower level, which will not be perceptible to the listener (or the phonometer). In this case it is useless to reduce the latter noise, as the composed noise will remain the same, being influenced by the higher-level noise only. 

Are the procedures employed the least invasive and traumatic available This practice is not only required by regulations, but is also sound scientific practice, since any induced stress will produce a range of responses in test animals that can mask or confound the chemically induced effects. 

The men who worked together almost night and day to devise efficient gas masks or means of submarine detection or methods of sound ranging were not workmen under the orders of a superior, but free associations of scientists with training in common or related fields of research and under the inspiration of a common patriotism. Precisely this is what is needed to achieve the victories of peace. Effective cooperation cannot be imposed from above by administrative authority but can only come by free democratic action of investigators themselves. (9). 

Independent of existing intra-lot variability, a sample size of six dosage units is generally recognized to suffice the needs of quality control (QC). In very early development less than six specimens may be used to create data, but as soon as possible tests should be run with at least n = 6. It is advisable to create statistically valid and sound data for manufacturing prototypes even at very early phases of development, in order to be able to identify formulations/batches with unwanted dissolution behavior. In the early phases of a drug product s development, formulations may not be of acceptable stability. This means that stability phenomena may mask... 

At five hours, the gas alarm sounded and everyone was supposed to mask. Z, however, didn t respond and wouldn t aceept help. For the next two days, he remained disoriented and hyperaetive, eonstantly trying to find a way out of the small outposf where he and his fellow volunteers were supposed to work together as a eommunieation team. 

Figure 2.1 (according to [Zwicker, 1982]) shows a masked threshold derived from the threshold in quiet and the masking effect of a narrow band noise (1 kHz, 60 dB sound pressure level masker not indicated in the figure). All signals with a level below... 

Lufti, 1985] Lufti, R. A. (1985). A power-law transformation predicting masking by sounds with complex spectra. J. Acoust. Soc. Am., 77 2128-2136. 

For non-stationary sounds the internal representation is best described by means of a temporal representation. The internal representation can be measured by means of a test signal of short duration. A schematic example for a single click (masker) is given in Fig. 1.3 where the masked threshold of such a click is measured with a second click (target). The masked threshold can be interpreted as the result of an internal, smeared out, representation of the puls (Fig. 1.3, excitation pattern). 

H. LINDEN I do want to caution you about oversupply of gas. I would say that we should start from the premise that maintaining the current market share of gas of about 25% is a laudible objective in that the old hierarchy of gas supply starting from conventional, both 1948 natural gas through synthetic gas, medium and high, LNG, masking gas, etc., will be cost competitive with an equivalent hierarchy of supplies of liquids and electricity. I hope this is a sound premise that we maintain the 25% market share of gas. 

Noise annoys people and causes tension among people. However, the types and levels are difficult to determine. Sometimes the noise of a different sound resonates at a frequency that masks other sounds. The noise level should be checked at all places before operations begin. 

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