**1. Introduction**

Studies have shown that aircraft noise has a great impact on the health status of populations residing in areas near air traffic, particularly citing cardiovascular diseases and the use of sleep and cardiovascular medications [1, 2]. In addition, researchers have concluded that there is a dose-response relationship between aircraft noise levels and blood pressure of the residents of an area near a military aircraft center [3].

However, most knowledge of the physiological effects of noise is generally obtained through animal experiment. To begin with, the open field test (OFT) is commonly used as a mechanism to assess the neurobehavioral effects of noise. Katz *et al*. [4] showed that white noise of 95 dB increased motor behaviors of rats in OFT and decreased their defecation after 1 h of acute stress. Food intake in OFT is reduced when rats are exposed to white noise of 95 dB, while their defecation increases [5]. In addition, the levels of neurotransmitters or hormones in plasma or brain may reflect the neurobiological effects of noise. Typically, the concentration of norepinephrine (NE) in the brain and cochlea of rats decreases after acute noise stress [6, 7]. Corticosterone levels in mice plasma have been shown to be significantly increased when exposed to acute noise for 10 min [8]. Male rats exposed to broadband white noise of 100 dB have been shown to have a significantly increased level of NE in the brain and corticosterone in plasma [9]. Furthermore, observing the morphological changes in neuronal cells can assess the effects of noise. Outer hair cell apoptosis has been observed in the cochlea of chinchilla after intense impulse noise exposure [10]. In addition, continuous noise stress has been shown to affect both degeneration of epithelial cells and apoptosis of stromal cells in the brain of pig [11]. We have not found any studies indicating that noise exposure induces morphological damage in the temporal lobe, the lobe related to perception and memory [12].

None of the aforementioned studies studied airport noise. Broadband white noise was diffusely applied in previous experimental studies to examine the physiological effects of noise. However, it is important to note that white noise in normal environment is almost nonexistent. In China, the aircraft-related weighted equivalent continuous perceived noise level (*L*WECPN) in many residential areas around airports overstepped the 75 dB limit stipulated by the "Standard of Aircraft Noise for Environment around Airport" policy. In this study, we thus sampled actual aircraft noise and played it back to laboratory rats. We then systematically studied their behaviors, plasma NE levels, and cell morphology of the temporal lobe.

Of course, there are some differences in the hearing sensitivity to different sound frequencies and circadian rhythms between rats and humans, which can bring variances in physiological effects under the same noise exposure. Therefore, if this study results are applied into humans, it should be further confirmed.
