# Evaluation of Noise Levels in a University Dental Clinic
## 1 Introduction  
Sound is a multidimensional concept that is characterized by measurable and audible changes in air pressure, perceived in both positive and negative ways. It can either be understood as noise (e.g., a nuisance) or present itself as noise, particularly when it transforms into it. People tend to habituate to noise exposure in different ways [1]. Among the different types of noise exposure, occupational noise is the one that has been investigated the most [2], followed by entertainment noise (e.g., music festivals, concerts, and bars) and headphone use with PMPs (personal music players) [3], and environmental noise (e.g., noise from road, rail, and air traffic, and industrial construction) [4]. If exposure to noise is chronic and exceeds certain levels, it can lead to negative health consequences, such as auditory and non-auditory health problems [5]. Auditory problems due to noise include various levels of hearing loss. Noise-induced hearing loss can be caused by an intense impulse sound occurring once (such as a gun-fire or explosion) [6], or by steady long-term exposure to noise levels higher than LA 75-85 dB--e.g., in industrial settings, including healthcare [7] and dental units [8]. World Health Organization (WHO) reports that 10% of the world's population is exposed to soundpressure levels that could potentially cause noise-induced hearing loss [9]. Hearing loss is the 13 th most important contributor (2-6% of the total number) to the global years lived with disability [1; 10; 11]. In about half of these people, auditory damage can be attributed to exposure to intense noise [12; 13]. Accidents and falls are consequently associated with undiagnosed hearing loss, especially in the elderly, with increased mortality [14]. Changes in sound perception that cannot be attributed to an external source, such as in hearing ringing, called tinnitus, often follow acute and chronic noise exposure and persist for extended periods [15]. Tinnitus affects the quality of life through sleep disturbances, depression, and inability to sustain attention [15]. The characteristic pathological feature of noise-induced hearing loss is the loss of auditory sensory cells in the cochlea [1]. Because these hair cells cannot regenerate in mammals, no remission can occur [16]. So, the prevention of noise-induced hearing loss is the only option to preserve hearing and avoid social discomfort [17]. Additionally, noise exposure has been linked to non-auditory health effects, including annoyance [18] and sleep disturbance, with consequent daytime sleepiness [19], which further leads to patient fear [20] and stress-related outcomes in healthcare settings [21], increases the occurrence of hypertension and cardiovascular diseases [22; 23], elevates cholesterol [24] and impairs cognitive performance [25]. It also leads to extreme stress responses [26], communication and concentration difficulties, mental fatigue, and a decline in efficiency/effectiveness [27]. Finally, noise annoyance in the workplace might be accompanied by negative responses, such as anger, displeasure, exhaustion, and burnout [28; 29]. Healthcare units are considered noise-sensitive facilities [5]. Since the 1960s, hospital noise levels have increased by about LAeq 10 dB [30]. Noise levels in hospitals are now typically more than LAeq 15-20 dB higher than those recommended by WHO [31], leading to noise-induced stress linked to burnout, diminished well-being, and reduced work performance for employees [32; 33]. Annoyance, irritation, fatigue, and tension headaches are also assigned to noisy healthcare workplace environments [34]. Noise also affects speech intelligibility and could, therefore, lead to misunderstandings that result in clinical errors [5; 32]. Among healthcare professionals, dentists are exposed to sounds from a variety of sources within the office, mainly from equipment and tools in use. Additionally, there are verbal interactions with assistants and patients that may be at a louder level than ordinary conversation.