Sanple Rate and Bit Depth

[wiiawiwb]

My SONY PCM M10 allows me the option to choose the SR and BD. Choosing the highest combination (96kHz/24bit) results in ~15 of hours to record. Choosing a lower option (48kHz/24bit) results in ~26 hours to record.

 

What settings are you folks choosing when you record in the field?

[MIB]

Varies by situation.   I have a couple kinds of recorders each with slightly different capabilities.   

 

My "carry" recorder is an Olympus DS-71.   I run it at PCM (essentially CD) quality.    If nothing has happened that I want to revisit, I'll stop the recording and delete it every 1-2 hours.   If something does happen, I stop the recording immediately (so the sound is at the end of the recording, easier to find later), move to a new folder, and start recording again.  

 

I usually have 1-2 small Sony recorders as well when I'm camping.   These are older ICD PX820s.   While the Olympus seems to record better, the Sony has a better voice-activated-recording mode.   Tradeoffs.   The Sony recorders have 4 settings, SHQ (essentially CD quality), HQ, SP, and LP.   My ears don't notice a difference in the 3 "denser" settings.    I generally carry two for camp.  I set one up in voice activated mode at SHQ quality so that anything loud enough to trigger recording is recorded as well as possible.   It may not help me, but there might be someone with better ears or better software who can do something with it I can't.   That recorder, in that mode, usually runs about 14 hours on a set of a batteries before they go dead and typically gives me 5-20 minutes of recording to review.   The other one is set in regular recording mode at SP quality.   I temporarily lost one last year and had to go back a week later to find it again.   It recorded for about 2-1/2 days non-stop (and got some interesting sounds) before the batteries died.  

 

I've started to fuss around with a Tascam which uses removable / larger SD cards and, if programmed right, will record while being powered from an external source.    That will expand my capability quite a bit but I'm not quite ready to roll with it in the field.  

 

I suspect to some degree the microphone used has more impact on the quality of the recording than the settings used on the recorder.    High quality nothing is still nothing.   I have been using Olympus mics for a few years.   Recently I stumbled over Edutige ETM-001 omnidirectional and ETM-008 directional mics.   I think they may be better yet. 

 

MIB

[wiiawiwb]

Correct me if I'm wrong but I think CD quality is 44.1mHz/16bit.

 

Is it fair to say that I should try to record at the highest quality as long as the field recording time won't exceed the recorder's maximum recording time?

[MIB]

Pretty much.     Recording time may be limited by battery life, the third corner of that triangle.    That can depend on whether you're staying with the recorder or caching it somewhere for retrieval later.  

[gigantor]

We use MP3 file format because it allows you to control the bit rate in addition to the frequency sample rate. This has great impact on file size, thus recording time and storage needs. Not sure if the model you use allows this, I use a Tascam DR-05 ($99).

 

IMO, we don't need CD quality to record a BF...  I thought about the sounds that are possible to capture:

 

1) Howls / Screams: You're not recording it for an opera performance and the sound is continuous. I guess the high frequency could get up to 10 kHz being very open minded. The bit rate can be lower because the sound is continuous and long, you will not miss it. 320k bps is completely unnecessary for this.

 

2) Speech: The recommended settings for human speech are only 6 kHz @ 45k bps.

 

3) Infrasound: It has a frequency from 0.1 Hz to about 20 Hz.

 

One important thing to know is that any compressed digital recording (i.e. MP3), when played back, can reproduce about half the frequency in the recording. ( Nyquist-Shannon sampling rate theorem). So a recording @ 44.1 kHz will only be able to playback at 22 kHz. For our purposes, this is more than enough.

 

CD quality is 320k bps @ 44.1 kHz

 

I use MP3 with 192k bps @ 48 kHz  sample rate, and even that is way overkill, I often think of reducing the bit rate lower.

 

Hope this helps.

 

[Explorer]

I use the same settings as Gigantor (192 bps @ 48 kHz) with MP3 file format and have the same recorder (Tascam DR-05).

 

I am satisfied with the quality of my recordings.  The improvements I need to make are on wind and background noise reduction.  I need to buy one of those wind noise reduction adapters.

 

With these settings, there is plenty of room for days of storage.

 

Although, I usually just record 3 nights in a row and the limitation is batteries.  The recorder will completely use up 2 AA Energizer Ultimate Lithium batteries in 3 nights (~21-24 hours).