Intensive care units (ICUs) have important but challenging sound environments. Alarms and equipment generate high levels of noise and ICUs are typically designed with hard surfaces. A poor sound environment can add to stress and make auditory tasks more difficult for clinicians. However few studies have linked more detailed analyses of the sound environment to nurse wellbeing and performance. This study is aimed at understanding the relationships between objective acoustic measures and self-reported nurse outcomes. Two 20-bed ICUs with similar patient acuity and treatment models were tested: A recently built neurological ICU and a 1980s-era medical-surgical ICU. The medical-surgical ICU was perceived as louder, more annoying, and having a greater negative impact of noise on work performance, health outcomes, and anxiety as compared to the neurological ICU. Surprisingly, there were little differences between two ICU sound environments based on traditional overall noise measures. The objective differences between the occupied sound environments in the two units only emerged through a more comprehensive analysis of the "occurrence rate" of peak and maximum levels, frequency content, and the speech interference level. Furthermore, mid-level transient sound occurrence rates were significantly and positively correlated to perceived annoyance and loudness levels.

Fixed and rotary wing aircraft operations can have a significant impact on communities in proximity to airports. Simulation of predicted aircraft flyover noise, paired with listening tests, is useful to noise reduction efforts since it allows direct annoyance evaluation of aircraft or operations currently in the design phase. This paper describes efforts to improve the realism of synthesized source noise by including short term fluctuations, specifically for inlet-radiated tones resulting from the fan stage of turbomachinery. It details analysis performed on an existing set of recorded turbofan data to isolate inlet-radiated tonal fan noise, then extract and model short term tonal fluctuations using the analytic signal. Methodologies for synthesizing time-variant tonal and broadband turbofan noise sources using measured fluctuations are also described. Finally, subjective listening test results are discussed which indicate that time-variant synthesized source noise is perceived to be very similar to recordings. Nomenclature a k (t)= amplitude envelope of the k th fan tone a mean,k (t) = mean amplitude of the k th fan tone a mod,k (t) = amplitude modulation of the k th fan tone b(t) = broadband noise pressure-time history f k (t) = instantaneous frequency of the k th fan tone f mean,k (t) = mean frequency of the k th fan tone f mod,k (t) = frequency modulation of the k th fan tone k = fan tone index K = total number of modeled fan tones s(t)= total recorded pressure-time history s k (t) = pressure-time history of the k th fan tone t = time z bb,k (t) = baseband-modulated analytic signal of the k th isolated fan tone z k (t) = analytic signal of the k th isolated fan tone

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Nurses do not always have visual access to their patients in hospital corridors. During these times, lack of proper monitoring of auditory cues can potentially delay nurse response time and disable early detection of complications. Particular acoustic characteristics of hospital sound environments such as reverberation time can be highly detrimental to nurses' sound-based task performance. In previous studies, the effects of surface materials on temporal characteristics of reverberant corridor sound environments have been studied. However, little is known about the relationship between floor-plate shapes and temporal characteristics of reverberant corridor sound environments. The main goal of this study was to statistically examine the relationship between floor-plate shape and temporal characteristics of reverberant sound environments in inter-connected nursing unit corridors by conducting floor-plate shape analysis, acoustic simulation studies and field measurements. Overall, the findings suggest the potential effectiveness of acoustic simulation programs in predicting the temporal characteristics of reverberant sound environments in inter-connected hospital corridors. Based on the acoustic simulation analysis, reverberation time was significantly correlated with two floor-plate shape metrics: visual fragmentation and relative grid distance.

Simulation of aircraft flyover events can facilitate psychoacoustic studies exploring the effects of noise generated by future aircraft designs. The perceived realism of a simulated flyover event may be impacted by the perceived realism of the synthesized fan noise of the aircraft engine. Short-term fluctuations in tonal amplitude and frequency are important cues contributing to that perception of realism, but are not accounted for by predictions based on long-term averages. A new synthesis method has been developed at NASA Langley Research Center to generate realistic aircraft engine fan noise using predicted source noise directivities in combination with short-term fluctuations. In the new method, fluctuations in amplitude and frequency are included based upon analysis of static engine test data. Through psychoacoustic testing, this study assessed perceived effectiveness of the new synthesis method in generating realistic fan noise source. Realism was indirectly assessed by judging the similarity of synthesized sounds (with and without fluctuations) with recordings of fan noise. Results of ANOVA analyses indicated that subjects judged synthesized fan noise with fluctuations as being more similar to recordings than synthesized fan noise without fluctuations.