21 research outputs found
Annoyance due to modulation noise and drop-outs in magnetic sound recording
Get PDFIn addition to a constant background noise, sound recordings on magnetic tape may also suffer from modulation noise and 'drop-outs'. The level of the modulation noise is proportional to that of the signa!. Modulation noise is more readily audiblein recordings of solo instruments than in orchestral music; listening tests have shown that for the flute the audibility threshold lies at a signal-to-noise ratio as high as 40 dB. The frequency with which drop-outs occur is a matter of tape quality. Listening tests have been carried out to determine the annoyance caused by drop-outs as a function oftheir duration, the degree of attenuation and the frequency of occurrence. The results of these experiments have been applied in the DAMA annoyance meter, which can measure these quantities for an audio tape and assign a quality rating to it
A pitch follower for speech signals
No full textOscillograms of a speech signal show, during the voiced parts, a distinct periodicity, which is a measure for the fundamental. The shape of this fundamental is an important datum in phonetic research. The present article describes the result of an investigation on the possibility of deriving this periodicity pitch from the speech signal on the basis of a time measurement. The instrument designed for the purpose can be divided into 3 parts: 1. A pulse generator, which fires at the highest tops of the speech signal. 2. A periodicity finder, also called an interval screen, which determines on the basis of the criterion that the mutual equality of two adjacent intervals between the highest tops must lie within +/- 10%, that a signal is periodic (voiced). 3. Some error-correcting circuits, which are necessary to cancel the consequences of jumps in the periodicity greater than +/- 10%
