Noise

About: Noise is a research topic. Over the lifetime, 5111 publications have been published within this topic receiving 69407 citations. The topic is also known as: Мопсы танцуют под радио бандитов из сталкера 10 часов.

Ambient noise and the design of begging signals

Abstract: The apparent extravagance of begging displays is usually attributed to selection for features, such as loud calls, that make the signal costly and hence reliable. An alternative explanation, however, is that these design features are needed for effective signal transmission and reception. Here, we test the latter hypothesis by examining how the begging calls of tree swallow (Tachycineta bicolor) nestlings and the response to these calls by parents are affected by ambient noise. In a field study, we found that call length, amplitude and frequency range all increased with increasing noise levels at nests. In the laboratory, however, only call amplitude increased in response to the playback of noise to nestlings. In field playbacks to parents, similar levels of noise abolished parental preferences for higher call rates, but the preference was restored when call amplitude was increased to the level that nestlings had used in the laboratory study. Our results show that nestling birds, like other acoustic signallers, consistently increase call amplitude in response to ambient noise and this response appears to enhance discrimination by receivers. Thus, selection for signal efficacy may explain some of the seemingly extravagant features of begging displays.

Benefits of linear amplification and multichannel compression for speech comprehension in backgrounds with spectral and temporal dips.

Abstract: People with cochlear hearing loss have markedly higher speech-receptions thresholds (SRTs) than normal for speech presented in background sounds with spectral and/or temporal dips. This article examines the extent to which SRTs can be improved by linear amplification with appropriate frequency-response shaping, and by fast-acting wide-dynamic-range compression amplification with one, two, four, or eight channels. Eighteen elderly subjects with moderate to severe hearing loss were tested. SRTs for sentences were measured for four background sounds, presented at a nominal level (prior to amplification) of 65 dB SPL: (1) A single female talker, digitally filtered so that the long-term average spectrum matched that of the target speech; (2) a noise with the same average spectrum as the target speech, but with the temporal envelope of the single talker; (3) a noise with the same overall spectral shape as the target speech, but filtered so as to have 4 equivalent-rectangular-bandwidth (ERB) wide spectral notches at several frequencies; (4) a noise with both spectral and temporal dips obtained by applying the temporal envelope of a single talker to speech-shaped noise [as in (2)] and then filtering that noise [as in (3)]. Mean SRTs were 5–6 dB lower (better) in all of the conditions with amplification than for unaided listening. SRTs were significantly lower for the systems with one-, four-, and eight-channel compression than for linear amplification, although the benefit, averaged across subjects, was typically only 0.5 to 0.9 dB. The lowest mean SRT (−9.9 dB, expressed as a speech-to-background ratio) was obtained for noise (4) and the system with eight-channel compression. This is about 6 dB worse than for elderly subjects with near-normal hearing, when tested without amplification. It is concluded that amplification, and especially fast-acting compression amplification, can improve the ability to understand speech in background sounds with spectral and temporal dips, but it does not restore performance to normal.

Habituation and dishabituation to speech and office noise

Abstract: The authors examined whether background noise can be habituated to in the laboratory by using memory for prose tasks in 3 experiments. Experiment 1 showed that background speech can be habituated to after 20 min exposure and that meaning and repetition had no effect on the degree of habituation seen. Experiment 2 showed that office noise without speech can also be habituated to. Finally, Experiment 3 showed that a 5-min period of quiet, but not a change in voice, was sufficient to partially restore the disruptive effects of the background noise previously habituated to. These results are interpreted in light of current theories regarding the effects of background noise and habituation; practical implications for office planning are discussed.

Responses to noise in urban parks and in rural quiet areas

Abstract: Nowadays the protection of quiet areas is an issue of increasing importance, as also recognized in the European Directive 2002/49/EC on the environmental noise [1]. Dealing with the demanded protection of quiet areas, it is important to characterize the soundscape of these environments properly, taking into account the multidimensionality of the individual perception which includes the effects of non-acoustic factors on subjective evaluation, such as visual impression and matching the personal expectation of the environment with the actual experience. This paper describes two experimental investigations carried out recently in Italy. The first deals with noise surveys and collection of subjective appraisals of three urban parks in Naples and the second consists of laboratory listening tests where sounds recorded binaurally in countryside parks have been mixed with sounds from some type of sources at different signal-to-noise ratios and played back by headphones to a group of subjects. The results obtained show that the subject's expectation to hear a sound in a specific environment, that is its congruence with the environment where it is heard, influences the corresponding annoyance. In particular, the more the sound is congruent with the expectation of the park, the less is the evoked annoyance and, conversely, the more is its acceptability. Furthermore, the acceptability of the sound increases with decreasing of its level and detectability of non natural sounds.