The contractile effect of the outer hair cells, activated by the efferent nervous system has been proven to provide a protective effect against acoustic trauma. However, a 2006 study revealed a different protective mechanism for stress conditioning. The study revealed that the stressor (sound, heat, or stress) conditioning increases the receptibility to glucocorticoid, a kind of anti-inflammatory hormone. The effects of glucocorticoid thus mitigate the inflammation from an acoustic trauma that can lead to hearing loss. In fact, high doses of corticoids are often prescribed by physicians after an acoustic-trauma in order to mitigate the inflammatory response. Summarized, sound (or other stressor) conditioning is a pre-emptive medication against cochlea inflammation. It does not make the ear more resistant to noise. It reduces the inflammation caused by the acoustic trauma, which would cause subsequent damages to hair cells. While an anti-inflammatory medication would increase the quantity of anti-inflammatory hormone in the whole body, noise conditioning increases the number of receptors for the anti-inflammatory hormone, and only in the areas where it is much needed (i.e. cochlea). Physiological response

stressor (noise, heat shock or stress) conditioning activates hormonal glands: the HPA axis. Note that the HPA axis is associated to the immune system
this HPA axis activation results in the up regulation of glucocorticoid receptors (GR) in the cochlea and the paraventricular nucleus (PVN) of the hypothalamus. Note that the glucocorticoid hormone is a kind of immune-reaction-inhibitor, including the inflammation reaction.
TTS is also measured in decibels.In addition to hearing loss, other external symptoms of an acoustic trauma can be:

Tinnitus
Otalgia
Hyperacusis
Dizziness or vertigo; in the case of vestibular damages, in the inner-ear

Tinnitus
Tinnitus is described as hearing a sound when an external sound is not present. Noise-induced hearing loss can cause high-pitched tinnitus. An estimated 50 million Americans have some degree of tinnitus in one or both ears; 16 million of them have symptoms serious enough for them to see a doctor or hearing specialist. As many as 2 million become so debilitated by the unrelenting ringing, hissing, chirping, clicking, whooshing or screeching, that they cannot carry out normal daily activities.Tinnitus is the largest single category for disability claims in the military, with hearing loss a close second. The third largest category is post-traumatic stress disorder, which itself may be accompanied by tinnitus and may exacerbate it. Quality of life
NIHL has implications on quality of life that extend beyond related symptoms and the ability to hear. The annual disability-adjusted life years (DALYs) were estimated for noise-exposed U.S. workers. [20]  DALYs represent the number of healthy years lost due to a disease or other health condition. They were defined by the 2013 Global Burden of Disease (GBD) Study. The DALYs calculation accounts for life limitations experienced because of hearing loss as a lost portion of a healthy year of life. So the results indicate the number of healthy years lost by a group of people over a specific time period.