ARREGLO INSTITUCIONAL EN LA GESTIÓN DE LOS RECURSOS NATURALES:

The different types of hearing loss will affect the audibility and intelligibility or clarity of sounds on different frequencies. These levels or degrees of hearing loss are based on the measurement of pure tone hearing threshold which is the lowest intensity or volume at which a child or an adult person with normal hearing may detect sound in any specific range of frequency at least 50% of the time. The level of hearing loss is calculated on an average based on 5 separate frequencies in the better ear (Brown 2006:12). The higher the pure tone threshold reading is, the louder a sound must be in order to be heard and the more severe the loss is, the lower the graph will be plotted on the audiogram (Watson, Gregory & Powers 1999:3). The loss of intensity varies across frequencies although the impact is generally greater on higher frequencies. The intensity or loudness of sound perception is measured in decibels (dB) and the hearing level results are plotted on an audiogram on the vertical y axis in the range 0-120 dB from the softest sounds at the top of the audiogram to the loudest sounds at the bottom. The frequency, which is perceived as the low or high pitch of sounds is measured in Hertz (Hz) on the x axis in the range 125-8000 cycles per second from the lowest to the highest pitch. (Haynes et al 2006:288; Marschark 2009:34; Storbeck 2007:351).

Figure 2.2 below shows familiar environmental sounds such as leaves rustling, dogs barking, aircraft flying overhead and speech sounds and the positions of these sounds on the audiogram in terms of volume and pitch. Of particular significance for a child with hearing loss is the placement of the various speech sounds in terms of pitch and volume in what is called the ‘speech banana’, bearing in mind that normal conversational speech is about 45 dB (Brown 2006:12). Consonant sounds of speech are predominantly high in frequency and since consonants carry most of the speech information, a learner with a high frequency hearing loss may miss many essential parts of words and this will manifest in significant problems with speech reception and speech production (Watson et al 199:3). Consonants also act as breaking points,

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separating syllables and words from one another. Consonants are spoken more softly in terms of intensity with the result that they tend to get drowned out by background noises. Additionally, consonants are higher pitched than vowels and there is a tendency for hearing loss to increase at higher frequencies (Hound Dog Hearing 2002; Ross 2004:30-31). It is pertinent to note that the voiceless ‘th’ [θ] sound is the weakest sound in the English language and the ‘s’ is the most frequently used phoneme in the English language (Ross 2004:30).

Figure 2.2 Audiogram of familiar sounds

(Source: Mt. Scott ENT. Audiogram of familiar sounds 2011).

Table 2.1 below classifies the degrees or levels of hearing loss in decibels and in terms of the effects these levels of hearing loss may affect the ability to communicate, bearing in mind that communication is key to language acquisition. There are strong correlations between the degree of hearing impairment and speech development (Paul 2009:138).

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Table 2.1: Degrees of hearing loss

Degrees in decibels

(dB)

Classification of hearing loss Effect on communication

0-15 dB Normal hearing N/A

16-25 dB Slight hearing loss Can’t hear speech if someone is far away or there is background noise. Problems with clarity and hearing morphemes in tenses and plurals at the end of words e.g. work(ed); king(s).

26-40 dB Mild hearing loss May lose 26-40% of speech signal. Battles to hear soft voices or distant speech even if there is no background noise. May lose up to 50% of information in class discussions.

41-55 dB Moderate hearing loss May lose 41-55% of speech signal. May hear normal speech at short distances or face-to-face. Potential delays in speech production, syntax and lexical knowledge.

56-70 dB Moderately severe hearing loss

May lose 56-70% of speech signal. Only hears loud conversation at close range. Battles to follow classroom discussions. Increasingly reliant on visual cues. Possible significant language development delays and speech production deficits.

71-90 dB Severe hearing loss May lose 71-90% of speech signal and therefore cannot hear normal conversations. Must be spoken to directly, loudly and at close range. Global language delays. Will require early intervention. >90 dB Profound hearing loss 91% + loss of speech signal. Relies on visual cues

(sign language, speech-reading) as communication tools. Language development delay and intelligibility difficulties.

(Source: Adapted from Flexer 1994; Northern & Downs 1991; and Stach 1998, in Haynes et al 2006:289).

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The degrees of hearing loss are more specific than using the broad categories of ‘hard-of- hearing’ or ‘deaf’. However, it would be imprudent to evaluate the potential of learners based on their threshold scores alone because some learners with profound hearing loss may be able to speak, speech-read and interact more successfully in the learning environment than learners with less severe forms of hearing loss. This is because the degree of hearing loss and the effects of this loss on the ability to communicate effectively are also dependent on other factors, one of these being the age at onset of deafness. This is a very critical linguistic factor, particularly for educators (Haynes et al 2006:290).

In an unaided condition (without the cochlear external processors in place) the research participant’s pure tone auditory threshold reading indicated a profound hearing loss of 100dB or more in both ears, with the left ear showing a higher loss than the right ear. Even with the aid of bilateral cochlear implants and speech-reading, there are certain frequencies of speech sounds which are difficult for the research participant to discriminate. These aspects will be expounded upon later in the study.