Background & Objectives: Noise is one of the most detrimental factors in working environments that alongside other physical problems have adverse effects on the mental health of employees. Open plan offices such as banks are under the influence of noise pollution sources, which can have a negative impact on health and comfort of employees. This study aimed to identify the sources of noise pollution in the banks and the level of noise annoyance among their employees .

 Methods: A-weighted Sound Pressure Level measured in the banks by a sound level meter. Perefferd noise curve (PNC) and speech interference index (SIL) were calculated, prevalence of noise annoyance, effects and clarity of speech were determined using a questionnaire with a reliability coefficient of 0.88 completed by 175 employees of Hamadan banks .

 Results: Sound Pressure Level equivalent of the banks were 64.11 dB. The average value of SIL index was calculated 54.93 dB and PNC index were calculated 58.17 dB and 48.2 dB for banks working and not-working times, respectively. According to bank staff opinions, the main source of noise pollution was commotion of clienteles that reduce concentration and increase overall effort to understand speech of colleagues.

 Conclusion: Noise emission in the studied banks had a low frequency band. PNC, and SIL indexes are perfect indexes for describing the acoustics condition and control plan for open office environments .