"Variations in the speed of playback of a recorded signal resulting in pitch variations and distortions. Wow has to do with small speed variations resulting in a wobbling sound. Flutter deals primarily with quicker speed fluctuations. Wow is a slower form of flutter. The two cause audible distortions in the reproduced signal."


Hello guys, I have noticed some effects similar to the above description when playing digital music from my mobile phone attached to the car stereo.

I have been told that when the phone CPU is under stress, audio playback can suffer "wow and flutter"-like effect.

I thought that this typical analog-domain defect wouldn't exist anymore in the digital domain.

Can someone clarify?

"Variations in the speed of playback of a recorded signal resulting in pitch variations and distortions. Wow has to do with small speed variations resulting in a wobbling sound. Flutter deals primarily with quicker speed fluctuations. Wow is a slower form of flutter. The two cause audible distortions in the reproduced signal."


Hello guys, I have noticed some effects similar to the above description when playing digital music from my mobile phone attached to the car stereo.

I have been told that when the phone CPU is under stress, audio playback can suffer "wow and flutter"-like effect.

I thought that this typical analog-domain defect wouldn't exist anymore in the digital domain.

Can someone clarify?

No such thing in digital.

Digital data is fed to a buffer where it is clocked out at a fixed rate. Varitations in the clock rate can cause jitter which is heard as a coarsening of the sound. In any case, digital audio from a phone is highly compressed crap that sounds like crap no matter what.

Audio data tracks are 44KHz, 256Kbps, AAC quite-acceptable-format; of course the digital to analog conversion is not being done through an Apogee Ensemble but from a phone, but that's not the problem.

I was trying to understand how can "variations to the clock rate" happen..

Yes, and the CD data rate is 2 channels x 44,100 samples per second per channel × 16 bits per sample = 1,411,200 bit/s = 1,411.2 kbit/s. Quite a difference in data rate and sound quality.

Again, cell phone audio sounds the way it does because it is highly compressed with a very low data rate compared to CD.

Clock rates can vary due to a poorly designed circuit. The result is jitter.

Could it be that the difference with a computer playing music, is that the computer itself has a dedicated device (like a soundcard) doing the playback so even though the CPU is under stress, the playback continues smoothly, while a phone has not?

No, it is because audio at 256 Kb/s is extremely poor quality. It doesn't matter if it is playing from a computer or a phone. It is lousy audio.

Nah, I believe the problem is not about the media being played itself, assuming the well accepted theory that the difference between uncompressed audio & compressed audio above 192kbps is barely perceivable by human ear.

Of course audio quality produced by a phone output streamed to the car stereo is ridiculous compared to a low-end hifi home system.

However, as I've said, when the phone is not under stress, audio plays smoothly. When running multiple programs on the phone at the same time, say the GPS navigator, notoriously for being taxing, variations in playback speed can occur.

Well then you're talking about how memory and processing speed is allocated like on your home PC. It's an issue of shared resources.

Exactly.
Probably the phone is missing some dedicated hardware

Well don't expect dedicated hardware on a phone! Just get a separate player of whatever brand suits you and be done with it.

Well, yes, what should I expect more from a "toy"?

I was impressed and disappointed about a digital device suffering such a defect.

I have noticed some effects similar to the above description when playing digital music from my mobile phone attached to the car stereo.

Many CDs are made from original analog tape recordings. :D

Otherwise, it's probably just the warbling sound you get from a low bit-rate, as others suggested.

--Ethan