Hacker News Reader

Comment by jaxbot | Hacker News Reader

My main interest is in Bluetooth 5. Walking around NYC, in even semi-congested areas of Manhattan, my audio cuts out with my phone in my front pants pocket. I literally have to hold it in my hand or coat pocket in order to cut through the interference. Has anyone experienced improvement when upgrading in this regard?

View on HN

I constantly had this problem, especially at intersections, and actually read recently on twitter (I wish I could dig up the details!) that transmitters the MTA uses to communicate with trains occupy a similar part of the spectrum. This partially explains why the effects seem to be the most dramatic at intersections that happen to have trains beneath them.

It's all 2.4ghz. The 7 train uses 2.4ghz (literally WiFi I've heard) for CBTC. The other lines don't have train communication, but the bluetooth beacons on them and Transit Wireless (station WiFi) are on the same spectrum of course.

> My main interest is in Bluetooth 5

Bluetooth 5 does not help you here at all. Stereo audio is still done over Bluetooth classic which has not been updated since version 2.1

source: i work on bluetooth

Ah, damn. I'd heard from other sources when Bluetooth 5 was first coming out that increased bandwidth was part of the spec, so I was hoping that would resolve my congestion woes. 2.4ghz is unusable at some points in the city. It's rumored that's why the 7 train's CBTC setup took so much longer than planned.

Yes. Bluetooth low energy in Bluetooth 5.0 now supports two megabits per second data rate, up from the previous speed of 1 megabit per second. The problem is, none of that matters for audio, because audio is never sent over bluetooth low energy. It is sent over Bluetooth classic. The specification for audio over Bluetooth low energy is not out yet.

Not arguing with your knowledge, but how does the LDAC codec on Sony headphones work then? Is this a later standard or a crowbar?

A2dp optionally allows multiple codecs. Anyone can make their own. Codecs are negotiated at connection time and if the headphones and device both support a given codec, they can choose to use it. SBC is mandatory, all others optional, including ones you can invent later (even after the spec is final and in use).

Thank you, that's interesting.

I only have experience with original AirPods, but at home I've often made it really really far away before I realized my phone is on the other side of the house. It only seems to cut off when I go outside with the phone left inside and walk away from the house. I haven't had patience enough with previous BT headphones to see if this is unique, but with AirPods+iPhone the audio pauses when it loses signal, which is much preferable to just the audio cutting out.

Conversely, when I power on the microwave within a few seconds audio will cut out repeatedly until it's unlistenable with the phone in my pocket if I'm anywhere in the kitchen. I'm not sure of a workaround and I'm sure if this was common I'd find them unusable.

I feel like there are a few times when walking around a busy place I get what you're talking about. Thankfully, it's not a common scenario for me.

Airpods 2 do not cut out when the microwave is turned on now :D. I've also found the signal stronger and passing through walls a bit better.

You just made a great point for wired headphones that I have never considered...

Audio cutting out? Isn't that the automatic #1 consideration point for wired vs wireless headphones?

Maybe its luck, but I finally found a wireless mouse and BT headphones that I haven't got anything to complain about. Around 5 years ago I made the same test and came back to wired versions.

I suppose AirPods, with that price tag, must be much better.

What are they?

Logitech G305 and JBL 450BT. (Cheap stuff, but I live in LATAM so those things are quite costly...)

I have the same issue in semi-congested Seattle — it's the biggest downside to the AirPods, imo. I'm very interested in how the new ones perform.

I've heard anecdotally that the problem is not only interference, but physical surroundings: http://www.iphonehacks.com/2018/04/heres-why-your-airpods-or...

I received some first-gen Airpods as a gift recently.

I haven't really had problems downtown Toronto. I have had the odd blip, but no real cutting out or anything like that.

I have this exact problem all the time in downtown Toronto. There's a even a few intersections where I know it's going to be bad (University/Richmond, Yonge/Adelaide, Front/George). So obviously some signals at intersections interfere, but I've wondered if a replacement would help.

I'm usually on a bit of a different circuit than yourself, so there are a few variables in there as is.

I'm in Liberty Village where I never notice any issues and bus from there, up past King/Shaw, Queen/Ossington, Dundas/Ossington to Ossington Station. I debark at Sherbourne/Bloor and walk to Jarvis/Bloor. I think that stretch on Bloor is the only time I notice blips.

Last weekend I rode the King streetcar to Peter and walked north to Queen and didn't have any issues there, either.

Might be some hotspots around town, though.

Not sure if it's the same phenomenon, but I have to keep my phone in the front pocket on the same side as the BT receiver to completely avoid choppy audio, and that's when I'm walking completely alone with no one in visible distance.

EDIT: I'm referring to the BT 5 protocol in general, and not specifically AirPods. I've tried a few devices where I've experienced this.

How does that work with AirPods? My understanding is that both are receivers and they communicate with each other for sync.

Oh, sorry, I should have been more clear. I was referring to the BT 5 protocol, specifically, as that's what the comment I was replying to mentioned. I have this problem with all the BT 5 devices I've tried.

Does it matter what side the phone is on?

I keep my phone in my right pocket, but my bluetooth headphones have the transmitter on the left side. Even in my suburban backyard (mowing the lawn), they'll occasionally cut out when my body interferes too much. Every now and then, it'll get bad enough that I'll move my phone to my other pocket.

This ^. I've come to the same exact solution. which is weird as you'd think apple would have run into this issue themselves and fixed it before release

I'd guess that max bluetooth transmission strength is less than the maximum allowed by the FCC's spec for the 2.4ghz band (bluetooth and many other things use this). We'll probably just end up in an arms race of transmission strength until we hit legal limits.

Basically already done in Manhattan. If you want working internet in an apartment building, it has to be 5ghz at this point. Everyone's WiFi transmitters are cranked up to max to try to punch through the noise floor, plus all the city infra (7 train CBTC, the train bluetooth beacons, commercial/public WiFi, LinkNYC, etc)

That sounds awful. How do they not have problems with people boosting above maximum allowed signal strength? I probably would have tried that by now.

Never had this problem in a whole other city though (another continent actually, but iphone in front pants pocket too + airpods).

So the comment below about MTA signals might be on to something...

Reply on news.ycombinator.com