At RSS.com, all our shows are distributed in mp3 format. MP3s have been the most popular standard format for online digital music files since the nineties.
The MP3 audio format reduces file sizes by removing sound information that is very subtle and often typically imperceptible, such as frequencies that are outside the human hearing range.
While a musician or a sound professional may be able to detect very tenuous changes in sound quality, a non-trained individual like most of us typically will not be able to perceive any difference between studio master recordings and their high-quality mp3 counterparts.
In addition, most consumer-level devices such as bluetooth headphones, earphones, smart speakers, car sound systems, laptop speakers, smartphone and tablets offer a great sound quality yet they are not specifically designed to reproduce audio professionally, therefore in most cases they won’t reflect subtle details in audio quality.
For all these reasons, MP3 is today the de facto standard to distribute podcasts globally.
Within the MP3 format, however, there are several options to the final audio quality including bitrate, sampling rate.
As a rule of thumb:
The higher the bitrate, the bigger the audio file size;
The most popular sampling rate for mp3 files is 44.1 kHz;
Because bitrate, sample rate and number of channels influence the size of an mp3 audio file, it is important to find the right balance. It’s a trade off: you want your episodes to be high-quality, but also small enough so they can be downloaded faster and effectively from any device, including smartphones that may have limited data plans.
In addition, because podcasting is a global medium and your show has the potential to reach hundreds of million of people worldwide. In this context, smaller audio files are more suitable for new and emerging markets where the cost of mobile data is still prohibitive for most.
So what is the best tradeoff between audio quality and size?
It depends on whether your podcast contains mainly voice (talk-predominant) or mainly music (music-predominant).
Talk-predominant podcast [Most common]
The vast majority of podcasts feature one or more people talking for most of the duration of an episode, and they only include small portions of music, such as a short intro and outro, and some occasional background music. We call these shows talk-predominant podcasts. This category of shows fits the majority of podcasts worldwide. The audio quality recommendations for talk-predominant podcasts are the following:
Bitrate between 96 and 128 kbps
Sampling rate: 44.1 kHz
Channels: 1 (mono)
Notice that using 1 channel (mono) for talk-predominant podcasts as opposed to 2 channels, will most likely result in no noticeable changes in the audio quality to the untrained ear and it will also reduce the size of your episodes in half, for a faster and more efficient distribution.
If a podcast includes a significant amount of music or more music than talk (e.g. a show about classical music where some classical pieces are played), we call it music-predominant podcast. The audio quality recommendations for this type of podcasts are the following:
Minimum 128 kbps
Sampling rate: 44.1 kHz
Channels: 2 (stereo)
The main difference between talk- and music-predominant podcasts is that for the latter 2 channels (stereo) are recommended. Recorded music, in fact, often leverages stereo sound to offer a more immersive experience by balancing different sounds or instruments in different channels or speakers.
Audio quality on RSS.com
At RSS.com, we follow the aforementioned guidelines and we automatically encode all your episodes into mp3 at 128kbps, 44.1 kHz, stereo
The final quality resulting from our encoding process is in full alignment with radio and music industry standards, including (but not limited to), the Apple audio requirements for podcasts creators.
If you would prefer us to not process your episodes, just upload them in mp3 format encoded at 128kbps and 44.1 kHz, so your files will pass through our filters without any alteration.
In the case your show has very special needs in terms of very high audio fidelity, we can allow hosting your episodes with bitrate of 192kbps or higher in accordance with our pricing tiers for high-traffic podcasts. Feel free to reach out to email@example.com for more information.