Technology
Cochlear Implant technology is very complex and can be confusing at times.
It is however important for future recipients to understand some of the most important points in order to make the right decision on what product to choose.
There are many criteria which are important among the most important are:
Intensity(loudness)
Normal hearing listeners are able to hear sounds from very soft whispers to loud rock bands. This is defined as the dynamic range of hearing and the range is about 120dB from the softest to loudest sounds.
So far, Cochlear implant listeners have only been able to obtain a maximum of about 45dB with their cochlear implants, meaning that sounds outside that range need to be compressed or omitted. This means that sounds that are too quiet will be cut-off and sounds that are loud will be compressed, sounding distorted.
The Advanced Bionics Harmony system is capable of delivering upto 96dB of sound to cochlear implant users. This means that users of our cochlear implants are able to hear MORE SOUND naturally than compared to any other cochlear implants.
The importance of this feature has been demonstrated in two studies comparing cochlear implants with small IDR’s (35dB or 45dB) vs. large IDR’s (60dB or higher).
The study in Figure 1 represents two groups of patients, those patient using the CII Bionic Ear system with 60dB of input dynamic range, and the Nucleus 3G system using 35dB of input dynamic range.
The two groups of patients performed similarly in quiet environments, however as the environment became noisy (signal +10dB louder than Background noise) and even more noisy ((signal only +5dB louder than Background nois) the patients with a larger input dynamic range systems performed SIGNIFICANTLY BETTER than those with smaller input dynamic ranges.
Performance difference between High (60dB) and Low (35dB) dynamic range users whose performance was matched in quiet
Figure 1: Performance of patients using the CII Bionic Ear system (Blue) and the Nucleus 3G system (Yellow) as a function of louder noisy environments. (Spahr, et al., Ear and Hearing 2007:28 260:276)
The study in Figure 2 was based on fluctuating signals and noise sources to demonstrate results closer to real life situations with 3 different cochlear implant systems: the Advanced Bionics Auria, the 3G and Freedom System from Cochlear AG.
Users were matched in regards of Age, duration of deafness, speech test scores in noise and device experience.
The signal to noise difference was randomly changed from the signal being 15 dB louder to 15 dB less loud than the background noise (solid) or 10 dB louder to 10 dB less loud than the background noise (hash). Performance was measured at what how much the signal in dB had to be louder than the background noise, to still understand 50 % of the sentences.
The less loud the signal had to be in relation to the noise the better the performance in real live where we are constantly surrounded by background noise and signals of changing intensity.
Figure 2: Performance difference between Auria from Advance Bionics and 3G and Freedom from Cochlear AG. Hash color +/- 10 dB rove , solid color +/- 15 db. The lower the bar, the better the performance, eg Auria performs 4 dB better than Freedom.
Buchner et. al. 2007
CONCLUSIONS Subjects well matched by demographics and speech test (+10 dB SNR) showed statistically significantly differences on a roving presentation level test. The group using the Auria processor had the highest performance. The Auria (predecessor of Harmony) processor has the largest IDR and supports the dual action AGC system. It appears that these technical features convey a significant advantage when listening in real-life situations where both competing noise and varying voice intensity across a range of speakers needs to be dealt with. Since large differences were elicited from a well matched group attention needs to be paid to the methods used to assess performance of modern cochlear implant processors. The better performing subjects are returning scores which are encroaching on the area that might be considered normal hearing, an encouraging endorsement of modern signal processing technology.
Literature:
Spar A, Dorman M (2007) Performance of Patients Using Different Cochlear Implant Systems: Effects of Input Dynamic Range. Ear and Hearing:28:260-275
Hochmair-Desoyer I, Schulz E, Moser L, Schmidt M (1997): The HSM sentence test as a tool for evaluating the speech understanding in noise of cochlear implant users. Am J Otol 1997 Nov; 18 (6 Suppl): S83
Mülder H (2006): FM in Schulen. Information on FM Systems,
© Phonak hearing systems
Spectral (frequency)
Normal hearing listeners are capable of hearing many thousands of distinct frequencies. This allows normal hearing users the ability to discriminate sounds based on their subtle frequency differences (i.e. 2 different keys on a piano, a high or low pitch sound, etc). Cochlear implant users however until now have only had at most 22 distinct channels along their cochlea, making it difficult to discriminate different frequencies.
The Hi-Resolution 90K implant has only 16 electrodes that are placed inside the cochlea. But each of the 16 electrodes is connected to its OWN INDEPENDENT output power source. This feature allows for us to turn on all 16 electrodes at a time, and have them function independently.
This feature allows us to create 120 channels within the cochlea, whereas other systems can only make 12 or 22 channels. The benefits of this technology allows patient to hear better in noisy situation and music. As seen in Figure 3, cochlear implant users’ appreciation of music is significantly better when using the Fidelity™ 120 channel technology.
Music Appreciation Ratings with Cochlear Implants
Figure 3: Music appreciation ratings from users with cochlear implants. Users of the Fidelity 120 strategy have reported the highest level of enjoyment and pleasantness of music in comparison with other cochlear implant technologies.
Temporal (time)
The Hi-Resolution 90K implant allows for stimulation rates of upto 83,000 pulses per second. Faster stimulation rates have been shown to increase the performance for our cochlear implant users compared to slower rates. Our clinical studies have shown that higher stimulation rates have resulted in significant increases in performance for our patients.
As seen in Figure 4 below, patients using the HiRes high rate strategies PERFORMED SINGNIFICANLTY BETTER after 3 months when compared with users of slow rate strategies.
Performance of Patients using Conventional Low Rate Strategies vs. Hi-Res High Rate Strategies
Figure 4: Patient performance pre-implant and after 3 months using MLNT and PBK Phenome and Word scores. The results compared conventional strategies against HiRes high rate strategies.
Osberger and Robbins, Advanced Bionics Research Bulletin, 2005
Article: 
Cochlear Implant - Two Local Children Receive The Gift of Sound. (PDF)
