**1. Introduction**

Noise is defined as an undesirable sound, characterized by multiple amplitudes and frequen‐ cies that occur simultaneously in a nonharmonic fashion. It is increasingly common in several environments and often not considered harmful to hearing, but interferes directly in word comprehension and communication.

Speech recognition occurs in conjunction with acoustic, linguistic, semantic, and circumstan‐ tial cues. However, under favorable conditions, some of these cues may be disregarded. For the message to be transmitted efficiently, acoustic cues vary according to the situation and context of communication, such as in conversation and noisy environments [1, 2].

Speech comprehension is an important point to observe during audiological assessment, since it provides data on how individuals understand a spoken message in daily situations [3], which are generally associated with the presence of competitive noise. When presented with speech and competitive noise at the same time, even normal listeners often have greater difficulty hearing and understanding it [4]. These difficulties arise because several auditory channels are required to obtain speech recognition during the assessment process with noise, suggesting that more detailed sensory information is necessary in difficult‐to‐hear situations [5].

Assessment of speech perception is important in establishing the relationship between hearing ranges, using information obtained from audiological diagnostic procedures, and hearing per‐ formance, which is related to how the individual is developing functionally. For good speech perception, joint action of the auditory system is required. This involves the outer, middle, and inner ear, cranial nerve VIII, the retrocochlear portion, and the central nervous system [6].

During audiological assessment, speech comprehension difficulties can only really be observed with speech stimuli that represent a communicative situation [7], thereby providing important information on the capacity of the individual to recognize words in noisy environments [3, 8].

The conventional tests used to assess language comprehension are a microscopic view of auditory function [2, 9], and speech recognition evaluation in the presence of noise would be a more realistic way of assessing hearing [10, 11].

Otoacoustic emission (OAE) testing is a relatively simple, fast and noninvasive objective method. OAEs are defined as the release of sound energy from the inner ear when the cochlea is stimulated, reaching the external auditory canal. Sound waves are captured by a small probe introduced into this canal.

Their discovery contributed substantially to the creation of a new concept regarding the func‐ tion of the cochlea, demonstrating that they are able not only to receive sounds, but also to produce acoustic energy [12]. This phenomenon is related to cochlear micromechanics, and it is suggested that when OAEs are generated in the cochlea, there is a mechanically active com‐ ponent coupled to the basilar membrane through which the reverse process of sound energy transduction occurs [13]. This property has recently been attributed to outer hair cells (OHC) and is controlled by efferent auditory pathways.

Suppression is characterized by a decrease in both the amplitude and peak phase of the emission. Test‐retest comparison shows that the suppressive effects are repetitive and that suppressing OAEs is clinically useful in assessing and managing peripheral and central hearing loss [14]. Medial efferent fibers may inhibit this active contractile component of OHC, regulating low contractions with attenuation of rapid contractions, thereby decreasing the amplitude of OAEs, when they are affected by electrical, chemical, or noise stimulation [15].

The frequent complaints of speech recognition difficulties, primarily in noisy environments, even in those considered normal listeners from the quantitative standpoint, as well as discov‐ eries of the active role of the cochlea, specifically OHC, are sufficient to prompt the investiga‐ tion of new methods that can be used to help stimulate the structures responsible for speech recognition in situations of competitive noise.
