Annoying MP3 Artifact
I have a Tascam DR-40 digital audio recorder, which I had used to record a seminar (in MP3 64K) using a pair of Crown FS6 PZM mics. When I played it back, I noticed a very annoying artifact very similar to the sound one gets when fast forwarding or rewinding a tape while it is playing. It only occurred when the speaker was talking. I was told that the artifact was introduced because there was a certain level of distortion coming over the loudspeakers in the room, and the MP3 processing within my recording unit converted the distortion into a weird frequency.
So, I'm stuck with a recording which, while the speaker is very clear and easy to understand, there is an additional and VERY ANNOYING warbling sound accompanying his speaking. What is particularly frustrating is that I can't use a software like Audacity to try and remove it because this software (and I imagine others work on a similar principle) requires sampling a part of the audio stream that only contains the noise in order to get a differential. To make matters worse, I was told that the noise is too closely intermingled with the harmonics in the speakers voice, so just clipping everything in the apparent frequency range of the noise would cause the sound speaker's voice to appear muffled.
I have a couple of questions.
1. Does anyone have any ideas as to how I could clean up this recording (which is a VERY important recording)?
2. I just realized that there IS a 320K recording option
3. Does anyone know what SD card (and what the largest size is) that would work without causing any timeouts. Remember, I have a Tascam DR-40 digital recorder.
I just purchased a DR40 a week ago and recorded my first MP3 speech today. I have the same "artifact" throughout the recording. It is a high mid frequency metallic scratchy, squeally sound, similar to the sound created by a worn out cassatte tape. There was no loudspeaker in the room so that is a poor excuse for a poor, artifact-laden recording on MP3. I used the internal mics on the DR40.
As with your experience, the recorded voice came across strong and clear. The artifact is annoying. Needless to say, I expected a better MP3 recording.
In the process of preparing this message I discovered the optional quality levels for MP3 recording: 32 (which is what I ignorantly chose), 64, 96, 128, 192, 256, and 320 kilobits per second. I'm sure even setting it at 64 K bps would have eliminated the artifacts. It would have been nice if the manual provided a warning about the consequences of a low MP3 bit rate.
The manual states that an SD card up to 32 GB can be used. That is 16 times the values of recording time for a 2 GB card indicated in the manual.
This post comes years after the original thread was started, it's June 2015 now.
Having bought a DR-40 and used it for a year, my conclusion is that it's a great device. However, I too noticed the Artifact, and while not in a studio, my client's meeting room was not like Noiseland, centered in the building it's pretty much Isolated. I Set-Up the Recorder using the built in Mics. I find in a U-shape table meeting, inside on a tripod is the best back-up copy.( We run 3 ). This time though, I lowered the rate to 32 and sure enough, just as Gerald Mucci wrote, there present, was that worn out cassette tape sound. I was glad I ran a test recording and played it back. When I did, I just defaulted to WAV with it's big files. I went back and reviewed previous MP3 recordings with the DR40. and they were set at 128. I log my settings. It's an old guy thing. I will talk to Tascam about it, their support is in California, so one has to call at the right time. Who knows, they may have a Firmware Update that fixes that. I recently worked with a client that had 60 Tascam Recorders they had rented from a company for a weeklong conference. The problem of it not STOPing when the button was pushed was annoying. It would not finish writing the file. It turns out, the machines were 4 Firmware Updates behind! (The bail out by the way, was to quickly eject and re-insert the SD card. This apparently breaks the DO loop, as we used to say in Fortran days. ) Joe