HAs are not hi-fi. The frequency range is not very high.
Daryl, all of what you say in the last two posts is true. I don’t dispute any of it.
What I don’t believe is that you can send TV audio in the bandwidth I can sense over BLE without an order of magnitude more frequency range. Do the math.
The audio doesn’t have to be 44KHz CD quality to be “hi-fi”. From what I hear through my TV connector, the audio is at least 16 bits and at least 8KHz. Nyquist sampling frequency would have to be 16 KHz minimum. As I have said, I have a TV Connector and I’ve done enough audio engineering to know this frequency range is actually conservative. I can also tell it’s stereo.
You need 32 KBytes/sec to transmit that data and BLE has less than 8KBytes/sec if you stretch it and disable retransmissions.
The TV connector drops out in either ear, and we know the right HA is the only one that makes BT Audio connections, so it’s not A2DP BT.
The Sonova chip says “The integration of CEVA’s advanced Bluetooth Dual Mode IP into our wireless chip enables us to bring low power stereo audio streaming and data connectivity to our hearing aids…” which means Standard BT A2DP and HFP for stereo audio streaming and phone calls, and BLE for data connectivity for power level and program selection.
(EDIT) Sorry I didn’t realize that the Sonova chip was relaitve to the TV Connector directly. Some of that last paragraph doesn’t apply to the TV connector. (EDIT)
Neither BT Profiles nor BLE GATT profiles can perform one-to-many streaming.
Sonova also says they support client IP which would support a custom 2.4GHz protocol over Bluetooth physical-layer transport for true one-to-many receivers for TV Connector streaming.
So a Bluetooth symbol on a frequency range and a vague word-association with a multi-protocol chip does not imply that the TV Connector uses any of the available Bluetooth profiles when it flies in the face of all the information and empirical evidence. All the information except for a single graphic symbol taken out of context.
Haven’t read up on MFI, but Android ASHA has the basic bandwidth “at the expense of latency” (which I do not experience with TV Connector), but is CoC-based (“Connection Oriented Channel”), like a point-to-point TCP/IP socket. It does not support one-to-many broadcast transmission that the TV Connector supports.
In engineering we consider all the details. I just can’t draw conclusions from abstractions. I could still be mistaken, but all the evidence I’ve seen is to the contrary about the TV Connector and BLE.
And regarding the BT Symbol, show me where it says use of that symbol requires that the FCC Cert is for a strict BT profile or BLE GATT profile and those profiles only. FCC certs are for radiation levels, bandwidth occupation (in the case of frequency-hopping), and sideband emissions (part of radiation levels). They don’t certify or care about protocols.
I concede that the TV connector could use BLE GATT profiles for signalling. Perhaps this is what the Bluetooth symbol is for. But not for audio with one-to-many capability.
Thanks for your reply. In the reference about ASHA, there is the following:
It is strongly recommended that the central and peripheral support 2MB PHY as specified in the BT 5.0 specification. The central shall support audio links of at least 64 kbit/s on both 1M and 2M PHYs. The BLE long range PHY shall not be used.
Is that the bandwidth you are looking for?
Using the right (or left. as configured) is only because HFP and A2DP by definition do not support multiple connections. However, BTC is not used for TV streaming, MFi or ASHA. With my Opns, MFi works with either one or both HAs. Similarly the ConnectClip. Similarly the TV box. So in all cases, presumably specialized BLE / GATT profiles must be being used.
Regarding one to many, according to GATT | Introduction to Bluetooth Low Energy | Adafruit Learning System, one central device may be connected to multiple peripheral devices.
@haggis @darylm Sorry if I missed it earlier in your discussion but the subject of passing an FCC certification to get a BT logo seems to have come up a time or two. All I know about it is that I just looked it up at bluetooth.com but it appears from the following that the BT symbol/logo is a TRADEMARK and it is issued by the BT SIG and is only assigned on two bases (plural of basis): 1) the company involved is a BT SIG member, and 2) the product is certified by the BT SIG as qualifying for its designation.
https://www.bluetooth.com/develop-with-bluetooth/marketing-branding/
Streaming audio cuts out from both ears when the left stops talking to the right. From this article:
“The fundamental drawback of their approach is that they rely on a 2.4 GHz signal to transfer information between the hearing aids. The technical characteristics of the signal means that it is inefficient to transmit the signal in a straight line between both ears. Instead, the 2.4 GHz signal relies on reflections from walls and other hard surfaces when it’s transmitted from one hearing aid and received by the hearing aid on the opposite ear… Provided there are hard surfaces in the wearer’s immediate vicinity then the signals are transmitted successfully between the ears and the wearer enjoys a continuous high-quality streamed signal. The problem arises when there are no hard surfaces such as walls and ceilings to facilitate transmission between the ears, such as in large halls or outdoor spaces.”
More on this topic here:
–rex
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@haggis Take a look at this: SBO Hearing A/S TV Adapter TVA3 FCC ID 2ACAHTVA3, which is the FCC page for the Oticon TV Adapter. It appears the product was initially released using BT LE @ 1 Mbps / 4 mW, using GFSK, then revised to use FHSS @ 2 Mbps / 21 mW, using 2GFSK. It appears like it’s a modification of BT LE to get more BW, but using quite a bit higher power. (The first test report is for the BT LE version. The second test report is for the FHSS version.)
BLE may be “one-to-several” but it’s not “one-to-many (unlimited)” as the TV Connector is reputed to be.
People might find this interesting I googled Roger Pen and FCC id and came up with TX17-1V1
Then I found this: Sonova USA . Remote microphone for hearing impaired people TX17-1V1 FCC ID KWCTX17-1V1
It also shows the BT symbol.
Perhaps the logo is just an indicator of what frequency range the RF emissions are in? Or was provided by Sonova for whatever reason and just reproduced at the site providing the FCC info (which I take it is a commercial site, with all the ads, not the fcc.gov site).
Here’s an official list of FCC-assignable logos. It doesn’t include the BT symbol.
Those all seem to be literally logos that validate FCC approval. Seems like their website could use a key.
Under 1st two heading at the page I referenced there’s a link: FCC-Approved Equipment Labels for Part 15 and Part 18 devices
In the attachments list offered on the linked page, there’s a run-down of the usage of the labels and certification text that’s to accompany the logos. I thought the neat thing is that they consider what to do if the part is too small for a logo and the text, etc. There’s something about having an electronic label as an alternative.
I agree with you that it’s interesting that a BT logo is used in association with the Roger Pen radio frequencies and it would be interesting to know if the fccid site just decide to put it there or somehow Sonova had a reason to use it, i.e., the Roger Pen is really a classic BT device and that’s why you can have Roger Direct with the Marvels?! BT to BT? (sorry if I’m all mixed up on this-haven’t been following Roger Direct to Marvels very closely). If you had BT that only works between registered/licensed Phonak devices, can that get the BT logo? Doesn’t something that uses BT have to work with any other BT device that meets the respective opposite function (client vs. host)?
Apparently Bluetooth 5.1 (at least in QCA6390 implementation) supports “1 to many” (see features in link) https://www.qualcomm.com/products/qca6390
The word proprietary comes up regularly and the device is within the Bluetooth frequency range.
Appears manufacturers don’t have to call a device Bluetooth if it is.
Confusing
Yes this all is very confusing. I suspect at least some of it is intentional. One former forum visitor used the term magical features. I think the HA manufacturers like to promote the idea that their products have magical capabilities that can restore your hearing.
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BT 5.1 does do “one-to-many” but it’s actually “one-to-several”, definitely not “one-to-unlimited”.
The Phonak TV Connector material definitely says “one-to-unlimited” on no uncertain terms.
“With AirStream™ technology it delivers top rated sound quality streaming from any TV and stereo system¹. The TV Connector can simultaneously stream audio signals up to 15 meters to an unlimited amount of connected hearing aids.”
https://www.phonak.com/us/en/hearing-aids/accessories/phonak-tv-connector.html
I agree with what rex-Hawaii has posted. My conclusion after going down the rabbit hole of technical jargon and manufacturer claims is that Phonak is using Classic Bluetooth at 2.4 GHz to send the multiplexed stereo signal to one hearing aid. Classic only allows one simultaneous connection. This means that the first aid must demultiplex the channels and send the left to the left, and right to the right. I think the problem comes in with Phonak choosing to use 2.4 GHz for this job too. That signal does not travel well through your head, and needs to bounce of hard surfaces near you to get to the other ear. If my assumption is correct then one hearing aid will drop out more frequently than the other. And if your body gets in between the phone and the first aid, then both can drop out.
Here is an article from Signia that kind of explains the issue. Brand X is Phonak Marvel.
Comparison of streamed audio signal quality: what matters in the real world
From my understanding, Signia gets around this problem, but only partially. They use MFi low energy Bluetooth which can talk to both hearing aids at the same time. There is no need to send the signal from ear to ear. However, they still have to get it from your iPhone in your pocket to each hearing aid. So it is only a partial solution. I use the KS8 which is basically a Signia 7Nx. What I notice is that outside away from hard surfaces I get more frequent drop outs. And I notice that when the phone is in my right front pants pocked, I am more likely to get a left aid dropout.
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But as I described in detail in the other thread, I don’t think they’re using MFi BLE to talk to both ears at the same time, at least in conjunction with the streaming test they described in the article. Or I’m wrong and they’re just really sucky writers.
But on my KS8 (Signia) I can pop the battery door open on either aid and the streaming continues to the opposite aid. Seems conclusive that I get left channel and right channel music from my iPhone direct to each aid. And my iPhone pairs independently to each hearing aid.
After a little more research I fully admit you’re right. The Signia 7Nx series supports the MFi audio. It must be what they used in the “study”. Why don’t they come out and say they’re comparing MFi bilateral audio to unilateral BT A2DP? That’s what confused me.