Muffeled audio using Bluetooth headset

I am having bluetooth reception issues whereby those who speak with hear a muffled voice, although I hear them well. I also get the seemingly random Bluetooth drops, and get reconnected within 30 seconds, exactly. There is also a slight lag in transmission using voice commands, too, that didn't exist before. I believe I may have isolated a probable effect. First, the constants:

iPhone 4: 32GB, black with Bluetooth and WiFi on; using Plantronics Voyager PRO with BT version 2.1 (this headset is the same in use with my iPhone 3G [S] prior to and after updating to iOS4; no problems noticed with OS3 or 4; latter OS used during 1 week prior to upgrading to iPhone 4, can't recall any complaints from callers)

Home (Alameda, CA): 2.4GHz TimeCapsule for WiFi supplemented by AirPort Express, both with (802.11n)

Office (San Francisco, CA): Dual Band TimeCapsule for WiFi supplemented by AirPort Express with (802.11n)

Car: No added features

Symptoms: When at home or at the office, calls coming in or out generally reported to me as being muffled. When outside walking or driving in the car, with or without windows and/or sunroof open, no reported voice clarity issues by those with whom I am speaking using my Voyager PRO. No voice clarity issues without the Bluetooth, everything is fine in terms of call clarity, no call drops, no problems with proximity sensor. It does not matter whether WiFi is on or not. No problems or differences in clarity either way. Good to go outside and away from WiFi hotspot.

Discovery: When I turn off WiFi on the iPhone 4 at home or in the office, muffled voice issue goes away within 30 seconds (typical polling period). When I turn on the iPhone 4's WiFi, the muffled voice issue returns within 30 seconds. I even receive an audible signal on my headset! Leaving it on, I will walk out of the house (or the office) and within 30-60 seconds, the reported muffled voice issue goes away.

Conclusion: there appears to be some conflict between the Bluetooth and WiFi when in the range of a WiFi device serving up an Internet connection. Not sure if it is due to the antennas in the iPhone, or if it software related, or both.

I sincerely hope that this repeatable troubleshooting report helps in some way to resolve the issue that many of us are reporting.

bought my brother an iPhone 4 and everyday i have issues as he uses a bluetooth (Plantronics Voyager Pro) to talk on it.. VERY-VERY muffled sound quality.. i told him about it, told him to "RESET NETWORK SETTINGS", and for the rest of that day everything seemed fine. thinking it was the bluetooth, he went and exchanged it for a brand new one (same model Plantronics...) he never had sound quality problems with his previous phone and his bluetooth.

a week later, i bought myself an iPhone 4.. a lil relieved i'm not having as bad of signal/bars loss / antenna issues as i was expecting-after experiencing such issues while playing with the display phones in the apple store.. however, i (have the same model Plantronics Voyager Pro) am having the same issues of muffled sound quality while utilizing my bluetooth (while holding and especially NOT holding the phone).. @first i figured, well the bluetooth antenna is wrapped around the phone, maybe that's it? BUTT:i'm using the bumper and most of the time i'm not even holding the phone.. tonight i was talking on my bluetooth and after a nice 30min convo, the sound quality went bad!.. SMH :-/.. AGAIN, i thought it was my bluetooth.. so, i have another line/service/phone, i made the call on that phone and everything was perfectly fine! ughhh!!!... after talking for 5min, i made the call from the iphone to test it out and the sound quality was ok, again.. SMH!!!.. this is totally NOT ACCEPTABLE!.. will give the software update a chance!, if it doesn't come w/in 30days, or if it doesn't fix these serious issues, (so sad to say, but) RETURN!!!!

other than these serious issues, the iPhone 4 is soooo smokin' fast, i luv it! please please please, Apple, iPhone 4-don't fail me NOW!!!!!!

It seems this problem is way more popular than I thought. If I don't hear anything from Apple with in the next week, it's going right back. I just don't want to be stuck with this problem for the next 2 years. I use the Bluetooth constantly, so this is unacceptable.

Apple's iPhone bluetooth problems are not isolated. I thought Apple had better QA than this.

I'm a brand new iphone users finally making the switch from Windows Smartphones, and I have people telling me they can't hear me when I'm using my Jawbone. I have to use the earbuds for handsfree. How last decade is that?

At yesterday's event, Steve mentioned improvements to Bluetooth in iOS 4.1. (No details, of course.) Keep your fingers crossed.