Patent Application
20110098787
The present invention relates to generally to the field of cochlear implants and improvements in obtaining sound quality for cochlear implant patients. The present invention relates more particularly to an external processing unit of a cochlear implant which processes sounds from within the ear canal of the patient. The present invention relates most particularly to the improved placement of the microphone used with cochlear implants to take advantage of the Pinna Effect and the Ear Canal Resonance of the human ear.
Cochlear implants are used to help the profoundly deaf to hear. However, a major problem for cochlear implant users is the difficulty to hear speech in noisy environments such as restaurants and groups of people.
Cochlear implants typically consist of two main parts, an internal receiver unit and an external processor unit. The internal unit is surgically implanted posterior to, or behind, the pinna of the ear of the patient. The internal unit has at least one electrode that is inserted into the cochlea. The internal unit also includes an internal coil assembly which receives signals from the external unit which then are carried to the electrode and into the cochlea. The internal unit also includes a magnet which is used to hold the external unit against the skin on the outside of the head.
The external unit also includes a microphone and signal processing component, and an external coil assembly. The external unit also includes a magnet for suspending the external unit utilizing the field of the magnet contained in the internal unit. These are located on the mastoid region behind the ear of the patient.
Alternatively, the external unit, can be in the form of a behind-the-ear (BTE) configuration (similar to a hearing aid) with the external coil attached to the BTE by an electric wire. The magnet is contained in the external coil assembly to hold the coil against the skin on the outside of the head. The BTE is held in place on the ear.
Audio sounds are picked up by the microphone of the external unit and converted into electrical signals. The electrical signals are then processed by the signal processor of the external unit and then transmitted across the skin to the implanted internal processor/receiver unit. The electrical signals from the internal unit are carried to the electrode and into the cochlea. It is this electric current which directly stimulates the auditory nerve and provides the user with the sensation of hearing.
Usually, the microphone in the external units is located either on top of, or behind, the pinna of the ear. There are several problems with this placement.
Microphones pick up all sounds presented to the patient without any filtering of background noise or amplification of speech. As a result, the processor is required to attempt to attempt do this difficult task. The best processors use noise cancellation techniques to cancel low frequency background sounds and directional microphones to create a “cone of hearing” in the direction that the patient is looking while talking to the person they are speaking with. While this is somewhat effective, it is not the methodology that normal people use in distinguishing speech from noise and hence, not nearly as effective.
Whether in a mastoid or BTE configuration, cochlear implant patients have problems with external noises such as wind and movement of hair, glasses and hats since the microphones of the external processors are relatively exposed to the environment.
The location of the microphones also present problems for patients who attempt to use telephones. U.S. Pat. No. 7,167,572 (Harrison et al.) sought to improve upon this by providing a microphone which is placed within the concha of the ear. When a telephone handset is held against the ear, the phone seals against the outer ear creating a chamber wherein the microphone resides. This improves the acoustic response of a BTE system during telephone use. However, while placing the microphone in the concha aids in telephone use, it does little to help cochlear implant patients in noisy environments.
People with normal hearing hear very well in noisy environments and in groups of people. While background noise is present, they are able to hear voices quite well. The reason for this is the effect on sound of the natural anatomy of the ear including the outer ear, or pinna, and the ear canal. The pinna gathers and directs sound to the ear canal. It is especially effective in mid and high frequencies (up to 10-15 dB or 3 times increase in loudness).
The ear canal provides natural amplification by functioning as a resonate tube. The canal resonance effect can be determined by the wavelength of sound and the geometry of tube match. The formula for resonance within a tube is F=V/(4L) where V=the speed of sound (velocity)=344 m/s, and L is the length of the tube in meters. Since an ear canal is approximately equal to 25 mm, or 0.025 m, F=344/(4*0.025)=3440 Hz. When calculated over the audible sound frequency spectrum for typical ear canals (see
The effect of the pinna and canal resonance together are additive.
The present invention utilizes a cochlear implant with the microphone located deep within the ear canal so as to take advantage of the pinna effect and ear canal resonance effects. Such a placement of the microphone allows the sounds that the microphone picks up to be similar to those heard by a normal hearing person, thereby naturally amplifying the mid to high frequency speech sounds in relation to the low frequency background noise. This placement also eliminates environmental sounds such as wind noise, hair movement, etc. since the microphone is now concealed within the ear canal and sheltered from these. It also provides a much more effective and natural sound input to the processor, and better results for hearing speech over background noise.
The microphone may be located at any point within the ear canal but preferably as close to the tympanic membrane as possible to take more advantage of the resonance effect. Placement can typically be within 5 mm of the tympanic membrane. However, this may not be possible in some patients due to a difficult geometry of their canal and placement may be limited to 5 to 15 mm from the tympanic membrane. Even in these situations, the patient will derive substantial benefits from the pinna effect and some resonance, as well as having the reduction in wind noise, hair movement, etc.
The microphone placement in the canal may be used with either a mastoid or BTE style cochlear implant. An electric wire is connected from the cochlear implant processor to the microphone with sufficient length to place the microphone in the desired location within the ear canal. The microphone can be supported within the canal by the wire connected to the microphone if it is sufficiently stiff, or can be supported with means similar to supporting receivers in ear canals of hearing aid patients, such as a custom molded support structure, or a preformed, flexible support structure.
While the preferred method is to place the microphone in the canal, an alternate method is to place the microphone in the processor unit, with a flexible tube connected to it which is long enough to be formed and placed within the ear canal to gather sounds from within the ear canal and deliver them to the microphone. While there may be a slight attenuation (approximately 3-4 dB) of some frequencies within the tubing, this can be very useful for small diameter or difficult geometry ear canals for placing the point of sound pickup as close to the tympanic membrane as possible with the benefits still being far greater than the typical external microphone configuration.
The present invention may also include two or more microphones located within the ear canal. It may be used with cochlear implants with digital or analog processors, single or multiple electrodes, and single or multiple channels.
It should be readily apparent to those skilled in the art that this improved device may be used on any cochlear implant configuration for patients with profound hearing loss to improve their ability to understand speech against noise backgrounds and better hearing in general.
The above, as well as other advantages of the present invention, will become readily apparent to those skilled in the art from the following detailed description when considered in the light of the accompanying drawings in which like numerals designate corresponding parts in the several views.
The present invention can be used with any external processor which can be used with a cochlear implant. The microphone can be of any suitable type for use with cochlear implants, which include, but are not limited to single or dual microphones.
The flexible tubing or wire 28 can be made of any material which is suitable for use with cochlear implant devices, and should be of sufficient length to hold the microphone as close to the ear drum or tympanic membrane as possible, such as in a range of 2-20 mm from the eardrum, but preferably 2 mm.
Alternatively, when microphone 26 is located in the external processor 20, the flexible hollow tubing 30 can be made of any material suitable for use with cochlear implant devices, and the open or free end 30A of the hollow tube 30 should be of sufficient length to be placed as close to the ear drum or tympanic membrane as possible, such as in a range of 2-20 mm from the eardrum, but preferably 2 mm.
In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiments. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.
This application claims the benefit under 35 U.S.C. 119(e) of U.S. Provisional Patent Application No. 61/255,562, filed on Oct. 28, 2009 under the provisions of 35 U.S.C. 111(b) The contents of this provisional application are fully incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61255562 | Oct 2009 | US |
