Some of our audio guide clients have been having issues with loading tour commentaries using our software due to the way audio files have been encoded. They’ve been experiencing strange quirks with audio playback. Of course, these issues end up in the AudioConexus Help Desk and the problem is very easy to solve. This is a problem with the “bit-rate” that someone selected for the audio file.
What are Bit-Rates?
Bit-rates are somewhat mysterious things. The best way to think of a Bit-rate is “The amount of data transferred as audio in kb/s”. Bit-rates are normally expressed in kilo-bits per second, or 1000 bits of data per second.
With this definition, the higher the Bit-rate the better! Right? Well, that’s not always the case. In an MP3 format, different bit-rates are good for different things. Here is a break-down according to Wikipedia:
“32 kbit/s – generally acceptable only for speech
96 kbit/s – generally used for speech or low-quality streaming
128 or 160 kbit/s – mid-range bit-rate quality 192 kbit/s – a commonly used high-quality bit-rate
320 kbit/s – highest level supported by MP3 standard”
I’ve seen audio files claiming bit-rates in the 800s, however files claiming this are usually just transmitting a lot of extra “dead air” and not adding to the fidelity of a recording.
How Does Bit-rate Impact Sound Quality?
Typically, I find that you’ll notice a difference in sound quality between 32 and 96 kilobits per second, while 96kb to 128kb is less noticeable. The noticeable difference between 192kb/s and 320kb/s is a hotly debated subject. Some people claim to hear the difference in sound quality while others say there is none. Now that we know a little about Bit-rates themselves, why do some audio files sound great on your computer, but flop, pop, hiss and click on your audio guide device?
This issue is not a problem with the audio guide, but with the Bit-rate being used on the guide. All audio devices come with limitations in terms of what they can process. Most audio devices on the market are programmed and designed to be able to play either 128kb/s or 192kb/s. AudioConexus audio guides can process up to 192kb/s. When an audio file is programmed for a Bit-rate over that limit, a lot of strange things can occur as the device tries to keep up with the amount of information that it is being given.
- Decreasing or Increasing audio speed
- ‘hissing’ sounds
- Muddy or distorted audio
- Volume issues
- Error messages
Encoding Audio Files for Audio Guides
These issues can be resolved by re-working the Audio File to be 192kb/s or less. Most recording software will give this option when “exporting”, “finalizing” or saving the file to an mp3 format. In the long run, checking your sound file format and Bit-rate can save you a lot of hassle and time. Your customers will enjoy your tour with crystal-clear sound reproduction every time.