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Hearing Loss

SPEECH AND NOISE MANAGEMENT

Mr Nitish of age 42yrs visited our clinic a week back with a complaint of reduced understanding of speech since a year. When we were reviewing the history, it was found that he was identified as having Mild to moderate sensorineural hearing loss in both ears in 2017. When enquired, he said that he had not had a trial with hearing aids before and currently he felt that this was gradually worsening. He also mentioned that he was feeling anxious at work because it was a noisy environment and that he had stopped watching TV as he no more understood the dialogues.Another audiometry was done and he was diagnosed as having moderate sloping sensorineural hearing loss in both ears. Test findings was shared with him and he was counselled regarding how important usage of hearing aids is for him. Trial with Pure Charge and GO 5NX was done for both his ears and he seemed to be most comfortable and delighted. He took them for a 3 day home trial and then purchased them the same week. His major concern was that he was working in a place where there were many people and he was unable to focus and understand conversations in group meetings or conversations at home over the dining table. 

Let’s see how noise plays a role in speech understanding

It’s a noisy world, and noise continues to be a major issue for hearing aid users. Let us take a look on Noise management strategies, general guidelines for assessing patients hearing abilities in noise, the intended applications for the various noise reduction strategies, as well as when and how to implement them.

Let’s face it, our environment is noisy.

  • Noise is the 1st main complaint of all participating consumers when eating at restaurants. Individuals cannot even escape from the noise in their own homes, as noise is the number-one neighborhood complaint. Since normal-hearing people are subjected to considerable amounts of noise on a daily basis, it is not surprising that the number-one complaint of all hearing aid users is difficulty hearing in noise; almost half (49%) of those who return their hearing aids reportedly do so because of problems with background noise.

Normal-hearing people also encounter difficulty hearing in noise, but are better able to recognize or discriminate speech than those with hearing impairment. However, as the background noise or when distance is increase or when unfamiliar topics are introduced, the natural discrimination of speech decreases.The discrimination capacity in speech are often lost when someone has hearing loss and parts of phonemes might not be audible. Auditory coding (frequency resolution) also might not be as precise, which can result in stimulation of additional frequency areas within the cochlea, making it more difficult to differentiate among the sounds being heard.

  • A second problem for those with hearing impairment is the ability to detect changes in the duration of sounds (temporal gap discrimination).Older adults with hearing impairment often face other difficulties in addition to the above mentioned problems. Given the same hearing loss configuration, studies have shown that older adults perform worse on speech recognition measures in quiet than younger adults. In addition, older adults might experience more difficulty processing language in the presence of competing speech due to cognitive involvement.

With all of these factors that can contribute to hearing in noise problems, what approach are most clinicians taking and is there more that could be done?

Most clinicians are using audiograms and speech discrimination measures in quiet on a routine basis as assessment tools for their hearing aid clients. Results indicate that less than half of the hearing instrument specialists were routinely performing some type of speech in noise test, although hearing in noise has consistently been the number-one complaint from hearing aids users for years.

Addressing Noise Issue(s)

It is important to Identify the Source of the Hearing in Noise Problem

Although audibility can easily be predicted from an audiogram, speech recognition ability in quiet is a poor predictor of speech recognition ability in noise. Furthermore significant differences have been reported in the ability to understand speech in noise among hearing-impaired listeners with similar audiograms.

In order to address the hearing in noise complaints, it is important to measure hearing in the various auditory domains that can contribute to hearing in noise difficulties. In general, there are three domains for assessing these difficulties:

  1. Basic auditory function or the audiogram        
  2. Speech discrimination ability in quiet
  3. Speech discrimination ability in noise

Addressing the Noise issues

Audibility. Current American Academy of Audiology (AAA) guidelines recommend performing real-ear measurements (REM) as a tool for verifying hearing aid gain in adult patients. REM can be used to provide objective information regarding whether incorrect gain is a contributing factor in reported hearing in noise problems.

The gain values that the manufacturer recommends for a given hearing aid user in the fitting software assume the patient has an average-size ear canal. Therefore, if a given patient has a larger-than-average ear canal, they may not receive enough gain and could complain that speech is not loud enough or that noise is too loud due to a primary audibility issue. Likewise, if the patient has a smaller-than-average ear, the hearing aids may provide too much gain, resulting in everything being too loud, including noise.

In addition, audibility—especially in noise—can generally be improved by fitting hearing-impaired patients with two hearing aids instead of only one, when possible. Such benefits include better hearing in quiet and noise, better sound quality, better localization of sounds, and higher listening comfort in various situations.

Although some studies have shown an improvement in the ability to understand speech in noise when fit binaurally, there may not be an improvement in the actual acceptance of noise. Studies also have shown there is a small segment of the elderly population who may actually perform better on speech recognition in noise tests when fit monaurally due to possible binaural interference.

Overall background noise. If your patient is complaining about the overall level of background noise, the problem could be due to noise that is mixed in with the signal of interest or noise that is being amplified in other areas along with the signal of interest.

Noise that is embedded in the signal of interest. It is extremely difficult to develop a hearing aid algorithm that removes all of the noise embedded in speech without eliminating or distorting a portion of the desired speech signal. Most hearing aids on the market today have a noise reduction algorithm that uses modulation rate/depth or spectral subtraction to eliminate unwanted noise from the signal. Enabling noise reduction or increasing the noise reduction gain for the environment(s) in which the patient is experiencing difficulty hearing in noise can be especially helpful in improving listening comfort.

Noise that is separated from the signal of interest. Directional processing can be helpful when a patient complains that he/she is having difficulty hearing in noise, and the speaker or signal of interest is separated out from the unwanted noise. Directional microphones are the most effective noise reduction strategy in hearing aidsand are reported to provide a 3 to 4 dBSNR improvement in real-world environments with low reverberation.

There are several basic directional technology schemes that can be selected for a given hearing aid user. Fixed directionality is best at cancelling noise located behind the hearing aid user when the speaker or signal of interest is located in front of the user.

Adaptive directional processing can be helpful when a hearing aid user is confronted with multiple noise sources. With adaptive directionality, multiple noise sources in different locations can be cancelled out at the same time. There are several different ways in which hearing aid users can access the directional programs within their hearing aids. Users can change the programs manually by using a button located on the hearing aids or by using a remote control device.

Wind noise. Wind noise generated by random turbulent flow across the hearing aid microphone(s) can be a mere annoyance or a debilitating interference for hearing aid users. Research has shown that wind noise interference can vary based on the style of hearing aid, the processing being used, and the direction of the wind flow.As a general rule, the best way to reduce the annoyance of wind noise is to prevent it from entering the hearing instrument in the first place. Some custom device styles, such as CICs that fit deeper into the ear or remote microphone instruments in which the placement of the microphone lies within the contours of the ear, offer natural wind noise protection. Other hearing aid styles, such as BTEs, are more susceptible to wind noise.

Microphone mode is also important. With a directional microphone, the interfering wind noise that is generated very close to the microphone is sensed with high sensitivity while the desired sound from the far field is sensed with low sensitivity. Whenever there is a choice, the directional microphone on a hearing aid should not be used when wind noise is present. Thus, fitting a patient with a single microphone hearing instrument or utilizing a program with omnidirectional processing can reduce wind noise complaints.

In addition to the above options, many manufacturers offer software-based wind noise programs that are designed to reduce gain in the frequencies in which wind noise is detected. Possible issues with such wind noise reduction features are that they may detect wind noise when it is not actually present, or they may fail to detect wind noise when it is. The result can be annoying gain reductions at unwanted times, or lack of comfort in windy conditions.

Ambient noise. Although wide-dynamic range compression (WDRC) and/or directionality can be quite beneficial, they also can create a problem: ambient noise.

WDRC is used to restore audibility for weak sounds and simultaneously restore some of the normal loudness perception that is lost with recruitment. In order to accomplish this, more gain is applied to low-level input sounds than high-level input sounds, with input signal levels below the threshold of compression typically receiving linear amplification.

Loud sounds. If loud noises are intolerable, but all other sounds are okay, it is likely that the patient’s UCLs for at least some of the frequencies have been exceeded. Real-ear and coupler verifications of loud sounds are excellent ways to verify that loud sounds are tolerable to the patient. Measured results can be compared to the patient’s actual or predicted UCLs to adjust hearing aid gain and output.

Counseling and Setting Realistic Expectations

The main goals when fitting amplification are

  • to improve audibility and to increase the signal-to-noise ratio resulting in an overall improvement in speech understanding.
  • Even with amplification, some patients will still encounter significant hearing problems due to a damaged auditory system, reduced cognitive ability, and/or difficult auditory environment.
  • Therefore, it is important to use the subjective and objective test results to counsel the patient about realistic expectations. If the patient demonstrates a significant SNR loss, he/she might benefit from assistive listening devices (ALDs), aural rehabilitation/counseling, or computer-based auditory training programs in addition to amplification.

With all of the wireless hearing aids in the market today, many new ALDs have been introduced that can improve the SNR by offering direct connectivity to TVs, phones, iPods, or remote microphones.

In addition, studies have shown that, when hearing aid users attend group support programs on average they have fewer return visits and report their hearing aids to be beneficial in more listening environments than those who do not attend a group. Computer-based auditory programs also can be helpful in improving speech understanding ability in noise. 

While technology and training can help improve the SNR for hearing-impaired people, noise will always be an issue that even normal-hearing people have to contend with on a daily basis. The best option continues to be starting out with a good SNR by being selective about the environment when possible and manipulating the environment when necessary.

Clinicians can be most beneficial to their hearing-impaired patients by providing them with hearing tools—not just hearing aids—and these tools should include ALDs, counseling, and listening strategies.

Speech and Noise management is compactible with the following hearing aids:

  1. Fun/Run/Prompt products
  2. Intuis 3 products
  3. RIC/BTE/Custom 1PX ,2PX ,3PX,5PX and 7PX products
  4. RIC/BTE/Custom NX Products
  5. Pure Charge and GO NX/Motion Charge and GO NX Products
  6. Styletto1/2/3/5/7 series

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