Halachic Talking Part V
October 3, 2023Halachic Hearing Part II
October 3, 2023A. Background
In the previous section, we considered halachic talking. Specifically, how devices that utilize microphone and speakers are considered in halacha. As mentioned, the same principles apply to microphones, hearing aids and telephones and as such there are many sources as the halachic analysis of one can be applied to the other. Additionally, these devices have been commonplace for many years and there were many more opportunities to analyze their status in halacha. In this chapter, we analyze a relatively new device, the cochlear implant and in so doing, discuss the definition of halachic hearing. Even newer innovations in hearing aid technology allowed for new devices that do not utilize a microphone and speaker in the conventional sense and as such require analysis. Importantly, there are comparatively few sources analyzing their use but many of the sources discussed previously have consequences that apply to cochlear implants as well.
The ear is composed of an outer, middle and inner ear. The outer ear is composed of the auricle and ear canal; the middle ear of the tympanic membrane, ossicles and the middle ear space; and the inner ear which is composed of the cochlea, semicircular canals and internal auditory canals. The auricle is constructed in such a way that it catches incoming sound waves which are then funneled down the external auditory canal. The sound waves then vibrate the tympanic membrane which causes the ossicles to move resulting in piston-like effects of the stapes. That motion pushes the inner ear fluid around the cochlea which set up fluid waves that moves the organ of Corti. Movement of the organ of Corti results in the bending of the stereocilia which causes depolarization of the auditory message that travels through the hair cells via the cochlear nerve. The cochlear nerve transmits the message to the brain where it is perceived as sound.
Pathology resulting in hearing loss can be categorized into three groups. Sensorineural hearing loss involves the inner ear, cochlea or auditory nerve. The former group can occur due to a myriad of reasons including hereditary, congenital, toxic or autoimmune causes. Conductive hearing loss occurs as a result of limiting the amount of external sound that can access the inner ear. And some combination of sensorineural and conductive hearing loss.
Most pathological hearing loss can be treated with a traditional hearing aid, as described in the previous chapter. Complex hearing loss can require the use of more advanced hearing aids provided that the cochlea are still functioning. Bone conduction hearing devices can be used to treat patients suffering from congenital atresia of the ear canal, chronic ear infections or allergies exacerbated by standard hearing aids or single sided deafness. Most commonly, a bone anchored hearing aid (BAHA) where a small titanium implant is inserted into the skull and osteointeregrates is utilized. An abutment is attached to the implant with either a small portion remaining sticking out through the skin or with a magnetic abutment and so no portion is protruding. The external processor can be detached when not in use. The BAHA bypasses the outer and inner ear by picking up sound from the environment and sending vibrations through the bone to the inner ear[1].
A direct drive hearing device (DDHD) is used in patients that that suffer from limitation in either low or high frequency sound quality. A processor that contains external microphones, batteries and signal processing hardware sits behind the ear. As it picks up sound it encodes them and emits non-acoustic infrared or low power radio frequency induction signals. These signals are received by a lens which resides in the ear canal and makes direct contact with the umbo the malleus on the surface of the tympanic membrane. The lens converts the signal into scaled vibration which propagate through the middle and inner ear allowing for sound to be perceived[2].
The Esteem[3] active middle ear implant (AMEI), indicated in severe hearing loss, replaces the inner ear. As in natural hearing, sound causes the eardrum to vibrate which is then converted into electrical signals by the sensor. The signal is subsequently sent to a sound processor which adjusts and increases the intensity of the sound as needed to the specific patient. The driver then translates those signals into intensified vibrations which stimulates the cochlea in the inner ear.
Cochlear implants (CI) replace the cochlea and completely replace the organic ear. Similar to the ear the external microphone picks up sound waves which are then converted into electrical signals that stimulate the cochlear nerve. That signal is then transmitted to the brain where it is processed into what we perceive as sound. Significantly, as opposed to the devices described above, CI completely bypass the ear.
As we described in the previous chapter, traditional hearing aids, at least from a halachic perspective, are a question of halachic talking. More advanced hearing aids and the ones described above are fundamentally a question of halachic hearing. That is, traditional hearing aids function by use of a speaker that amplifies the surrounding sound. The question then becomes is the sound transmitted over a speaker considered synonymous with the sound leaving the person’s mouth. However, the devices discussed here do not utilize a speaker. Instead, they allow for sound to be transmitted by some other medium. It is then paramount to understand what qualifies as halachic hearing. The devices described all result in normal neurological hearing processes to occur. The difference lies in how the sound is received. The available halachic sources primarily discuss cochlear implants; we are not aware of any that discuss the other devices mentioned above. Thus, it is the purpose of the following chapter to determine how the sources discussed in the previous chapter regarding hearing aids and the few sources on cochlear implants pertain to the devices mentioned here.
[1] https://www.uptodate.com/contents/hearing-amplification-in-adults?search=hearing%20aids&source=search_result&selectedTitle=1~71&usage_type=default&display_rank=1#H3029744140
[2] Vaisberg J., Sound Quality Ratings of the Amplified Speech and Music Using a Direct Drive Hearing Aid: Effects of Bandwidth.