Tried looking at the tv connector info to see if it had frequency specs. No luck. Quick search found nothing either. Sorry
The technical data sheet I found for the Oticon Connect Clip gives the âAudio bandwidthâ as â80 Hz - 10 kHzâ with a footnote of âActual audio performance depending on clientâs hearing instrumentsâ.
The technical data sheet I found for the Oticon TV Adapter 3.0 gives the Audio bandwidth as â10 KH/stereo from input to hearing aidsâ. No lower frequency cut-off listed in that document.
The technical data sheet for the OPN S gives a fitting bandwidth of 10 KHz for the S 1 and 8 KHz for the S 2 and S 3. The same sheet lists various frequency ranges for the different âreceiversâ for the OPN when measured with either a Ear Simulator or a 2CC Coupler. The frequency range is given for the 4 power level receivers and two test devices - the low end is between 100 to 120 Hz with most combinations being listed at 100 Hz. The graphs presented in the doc also range from 100 to 10,000 Hz with a log scale used for the frequency axis. The response is typically falling quickly as the lower limit is reached âŚ
My guess is that the low frequency limit of the system (Oticon OPN hearing aids and any intermediary device) is actually set by the receiver in the hearing aid unless there is significant filtering in the TV adapter prior to the digitizer.
I have no idea of the frequency bandwidth and response curve of a typical amplified stethoscope. If the response curve extends below the limit of the hearing aid receiver, the hearing aid is the limiting device. That may be altered if the person using the hearing aids has good low frequency hearing and the fitting is open. Then high quality âclosedâ headphones that fit around the ear and hearing aid might actually work better. My OPN S 1 aids do not feedback with Beyerdynamic closed headphones that were typically used for studio monitoring - they have better low frequency response than the HA receivers. The amplified stethoscope would have to have an audio output sufficient to drive the headphones correctly over the frequency range of interest.
Searching the Thinklabs One site, I did find a list of the filters provided in the device. The low frequency cutoff can be as low as 20 Hz and as high as 100 Hz depending on the filter chosen. There is a comment in the description of the filter that cuts at 30 Hz that is relevant - âBass may be challenging for some third party headphones and other external devicesâ.
So the hearing aid receiver is probably the limiting factor, at least for the Oticon OPN S 1. Other hearing aids may have better low frequency response.
When comparing the CC to the TV Adapter, donât forget that the CC is very compact and requires no external power. Not so with the TV adapter. Same for the Taotronics BT Transmitter. If I were using a stethoscope, I would not want to be constrained by a bulky device or a power cord.
Also, anyone wearing hearing aids most likely has limited ability to hear frequencies above 8-10K, so it seems kind of meaningless to consider the upper frequency response.
The lower frequency response might be another matter. In Electronic Stethoscopes â Technology Overview, it says the following:
Frequency
The full range of human hearing extends from 20-20000 Hz. The accepted frequency range of human heart sounds is about 20-200Hz and the accepted frequency range of human lung sounds is about 25-1500Hz. Most of the electronic stethoscopes on the market offer Bell mode, Diaphragm Mode and an Extended Range mode. Extended Range is usually referred to as wide, extended, or organ mode. For the most part, each electronic stethoscope has a button or switch to change between modes. The button or switch for changing frequency or mode can be located on the chest piece, on a module incorporated in the tubing, or directly on the stethoscope unit itself.
When the stethoscopes are placed in these modes they have two potential behaviors, they either block out all sounds except for the defined frequency range or they allow all frequency ranges through but optimize the sounds in a defined frequency range. For the stethoscopes that we analyzed there was variety in the frequency ranges of the bell, diaphragm and extended modes, but in general bell mode was from 20-650Hz, diaphragm mode was from 20-2000Hz, and the extended range was from 20-1500Hz. The overall sampling frequency range on the evaluated stethoscopes was from 15-20000Hz. See each individual cut sheet for the specific unit frequency ranges reported by each manufacturer.
If I were a physician, I would concerned about my ability to hear the lower frequencies.
I have been using the Thinklabs unit for about 3 years with a pair of studio headphones. They are sort of useful, but pick up too much ambient noise, noise from holding the unit on the chest, noise from the headphone wire dragging over the patient, etc. Not really what I was hoping for I have called several times about bluetooth direct to mu Phonak HA, but am told they were working on it but got hung up in FDA approval 
Lanned could use a rolled up newspaper, but now the FDA can hold up something useful for years.
This is what my audiologist and I have been trying to tweak. The sound is distorted and soft - instead of âlub-dubâ it is more of a faint, tinny âclick/tap-dub.â I use Unitron Moxi Move R.
Jeff
Stethoscopes seem like a big challenge. I donât have firsthand experience but tried to gather some resources for a nurse practioner friend with hearing loss and posted them on my website: https://gatheringsound.com/electronic-audio-devices-phone-tv-computer-etc/