ReSound digital 5000 Hearing Aid
The ReSound digital 5000 was available first in BTE and ITE case styles, with dual microphones available in the BTE version. Throughout 1999 they introduced more case styles and more features. (See photos of the BZ5 aids on a real head) As of September, 2000, the Digital 5000 is available in all case styles including the tiny CIC sizes.
See the article on the ReSound Canta 7, for a newer ReSound product (as of May 2001). In 2007 ReSound introduced the AZURE, which builds on all of these predecessors, and which has some really neat new features.
The Digital 5000 was discontinued January 1, 2003.
We will discuss the most fully featured model of the digital 5000, the BZ5 dual microphone BTE instrument in this article. It has a wealth of features, including
ReSound's Digital Cochlear Dynamics® signal processing,
Fourteen bands of noise reduction,
Adaptive Feedback control,
Cell phone shielding, and more.
ReSound says that their signal processor is software based, using Fast Fourier Transforms, and that the software can be upgraded without replacing the integrated circuit chip. The software divides the signal spectrum into 14 bands and applies the type of compression dynamics in each band that the older analog ReSound hearing aids apply in two bands. This allows a more accurate representation of the hearing loss, and the digital signal processing allows more tricks to be played with the signals.
The top of the line BTE has two microphones connected to the signal processor through filter and delay circuits to allow exact matching of the characteristics of the microphones. The microphones are adjusted to match each other to within 0.25 dB at the factory. The microphones can be software set by the audiologist to cardioid, hypercardioid, bi-directional, or omnidirectional, depending on the user's preference. Different programs can have different microphone settings. For example, you might want to use bi-directional in the car, to hear front and back, but not to the sides, or cardioid in a restaurant where all the people you want to hear are in front of you.
Four "programs" are available, selectable by push button. The programs are set-up by you and your audiologist for situations important to you, such as "speech", "restaurants", "music", "telephone", or whatever. You change programs by pushing a button on the hearing aid. A neat feature is an audible beep, one beep for program one, 3 beeps for program 3, and so forth. Your audiologist can reprogram the hearing aid for different "programs" anytime you want. The some Centers gives unlimited free, reprogramming of your hearing aids, for as long as you own the aids. So you can change your mind, if your needs change.
The ReSound feedback control is set for your ears at programming time in your audiologist's office. The hearing aid listens to "quiet" and measures any feedback. It then computes the inverse of that feedback and applies that to a special anti-feedback filter, effectively canceling out the feedback. In addition, if a special circumstance causes feedback while the hearing aid is in use, such as when you put your ear next to a pillow, the anti-feedback filter will adjust for the new signal and after a few seconds, remove it also. (From a user's standpoint, if you do something to cause feedback, hold still until the circuit adjusts to remove it. Don't jerk away and try again, that will just give you the initial seconds of feedback again.)
The inside of the ReSound digital 5000 BTE hearing aid case is plated with a very thin gold shield to protect against cellular phone emissions. The problem of interference from cell phones is phone and hearing aid dependent. Not all hearing aid and cell phone combinations have a problem, but this is one good way of eliminating the problem.
The BTE instrument has a provision for Direct Audio Input for use with classroom transmitters and assistive listening devices. A boot is placed over the bottom end of the hearing aid, and connectors from external devices can be plugged into it. There are different connectors available for different uses, such as plugging it into a radio, or a theater listening system.
The multiband signal processor and noise control system is the heart of the ReSound digital 5000 hearing aid. Each of the 14 bands continuously adjusts for the input signal, bringing quiet speech sounds into the audible range and preventing loud sounds from being too loud for the damaged hearing system of the listener. The patient's audiogram and hearing comfort levels are entered into the hearing aid by a direct connection to a computer in the audiologist's office, while the patient listens to the results. After the initial programming, the patient is asked a series of "which sounds better" questions until each program is set. Later on, after the initial fitting, when the patient comes back for discussion and adjustment, all of these settings can be changed. Most offices can play a variety of background sounds, such as traffic noise, restaurant babble, music, and so on, while the patient is making these judgments about what is preferable.
The noise control circuits "listen" to the signal in each of the 14 frequency bands, trying to decide if the signal is speech or noise. The processor uses a statistical decision making process, deciding that continuous or repetitive signals are noise, and wide dynamic range sounds are speech. ReSound says that the processors are very fast, and can actually remove noise between syllables of speech. Note that you don't have to have the noise processing in all of your "programs", and that you can have different levels of aggressiveness in the noise removal processing in different "programs".
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