Alali Khaled A, Casali John G
Auditory Systems Laboratory, Virginia Tech, Blacksburg, VA, USA.
Noise Health. 2011 Mar-Apr;13(51):99-112. doi: 10.4103/1463-1741.77202.
A human factors experiment employed a hemi-anechoic sound field in which listeners were required to localize a vehicular backup alarm warning signal (both a standard and a frequency-augmented alarm) in 360-degrees azimuth in pink noise of 60 dBA and 90 dBA. Measures of localization performance included: (1) percentage correct localization, (2) percentage of right--left localization errors, (3) percentage of front-rear localization errors, and (4) localization absolute deviation in degrees from the alarm's actual location. In summary, the data demonstrated that, with some exceptions, normal hearing listeners' ability to localize the backup alarm in 360-degrees azimuth did not improve when wearing augmented hearing protectors (including dichotic sound transmission earmuffs, flat attenuation earplugs, and level-dependent earplugs) as compared to when wearing conventional passive earmuffs or earplugs of the foam or flanged types. Exceptions were that in the 90 dBA pink noise, the flat attenuation earplug yielded significantly better accuracy than the polyurethane foam earplug and both the dichotic and the custom-made diotic electronic sound transmission earmuffs. However, the flat attenuation earplug showed no benefit over the standard pre-molded earplug, the arc earplug, and the passive earmuff. Confusions of front-rear alarm directions were most significant in the 90 dBA noise condition, wherein two types of triple-flanged earplugs exhibited significantly fewer front-rear confusions than either of the electronic muffs. On all measures, the diotic sound transmission earmuff resulted in the poorest localization of any of the protectors due to the fact that its single-microphone design did not enable interaural cues to be heard. Localization was consistently more degraded in the 90 dBA pink noise as compared with the relatively quiet condition of the 60 dBA pink noise. A frequency-augmented backup alarm, which incorporated 400 Hz and 4000 Hz components to exploit the benefits of interaural phase and intensity cues respectively, slightly but significantly improved localization compared with the standard, more narrow-bandwidth backup alarm, and these results have implications for the updating of backup alarm standards.
一项人为因素实验采用了半消声声场，要求听众在60 dBA和90 dBA的粉红噪声中，在360度方位角内定位车辆倒车警报警告信号（标准警报和频率增强警报）。定位性能的测量指标包括：（1）正确定位的百分比；（2）左右定位错误的百分比；（3）前后定位错误的百分比；（4）与警报实际位置的角度定位绝对偏差。总之，数据表明，除了一些例外情况，与佩戴传统的被动式耳罩或泡沫或带凸缘类型的耳塞相比，正常听力的听众在佩戴增强型听力保护器（包括双耳声音传输耳罩、平坦衰减耳塞和随声级变化的耳塞）时，在360度方位角内定位倒车警报的能力并没有提高。例外情况是，在90 dBA粉红噪声中，平坦衰减耳塞的准确性明显高于聚氨酯泡沫耳塞以及双耳和定制双耳电子声音传输耳罩。然而，平坦衰减耳塞与标准预成型耳塞、弧形耳塞和被动式耳罩相比并没有优势。在90 dBA噪声条件下，前后警报方向的混淆最为明显，其中两种三凸缘耳塞的前后混淆明显少于任何一种电子耳罩。在所有测量指标上，双耳声音传输耳罩由于其单麦克风设计无法听到双耳线索，导致其在所有保护器中定位最差。与60 dBA粉红噪声的相对安静条件相比，90 dBA粉红噪声中的定位始终更差。一种频率增强型倒车警报，分别加入了400 Hz和4000 Hz的成分以利用双耳相位和强度线索的优势，与标准的、带宽更窄的倒车警报相比，定位略有但显著改善，这些结果对倒车警报标准的更新具有启示意义。
