3.1 Audio formats for mobile journalism

In mobile journalism, audio format has two meanings. The first is the programme format: the type of audio story, such as a news clip, a voicer, a package, a vox pop or a podcast episode. The second is the file format: the way the sound is stored on the phone, such as WAV, MP3 or AAC. A mobile journalist must choose the right programme format for the story and the right file format for recording, editing and delivery, so that the sound reaches the radio station, website or audience in good quality. Example: a reporter covering a county assembly sitting may file a 30-second voicer for the hourly radio bulletin as an MP3 and a longer interview as a WAV file for a weekend podcast.

Audio programme formats

• Actuality or clip: A short extract of a newsmaker speaking, usually 10 to 30 seconds, used inside a bulletin or another story.
• Voicer: The reporter's own voice reading a short report from the scene, usually 20 to 40 seconds, with no other voices.
• Wrap (voice wrap): A voicer that wraps around one clip: the reporter introduces, the clip plays, and the reporter closes.
• Package: A longer produced story, often one to four minutes, combining the reporter's narration, several interview clips and natural sound from the scene.
• Vox pop: A series of short answers from members of the public to one question, edited together to show a range of views.
• Two-way or live question and answer: The reporter answers questions from the studio presenter, recorded or live over a phone or app link.
• Interview: A recorded conversation with one guest, edited for length and clarity.
• Podcast episode: A longer audio programme published online for listening on demand, often as part of a series.
• Audiogram: An audio clip combined with a still image, a moving sound wave and captions, made for social media where much audio is played as video.
• Voice note: A short recording sent through a messaging app, used by some newsrooms to deliver news updates to followers.

Audio file formats

Sample rate, bit depth and bit rate

• Sample rate: The number of times per second the sound is measured. 44.1 kHz is the standard for music and podcasts, and 48 kHz is the standard when audio will be used with video. Both capture the full range of human hearing.
• Bit depth: How precisely each sample is measured. 16-bit is enough for finished audio, 24-bit gives more room for error during recording, and some newer wireless microphone kits and recorders offer 32-bit float recording, which protects against distortion when a sound is suddenly very loud.
• Bit rate: For compressed files, the amount of data used per second, measured in kilobits per second (kbps). Spoken-word MP3 files are commonly exported at 128 kbps or higher; lower rates make files smaller but can sound thin and watery.

Mono and stereo

Mono recordings carry one channel of sound and are standard for speech, interviews and news reports. Stereo carries two channels and adds a sense of space, which suits natural sound and music. Many phone microphones and adaptors record in mono; a mono recording exported as stereo simply plays the same sound in both ears.

Choosing the right format

Record in the highest quality the phone and app allow (WAV or high-quality AAC, 48 kHz), edit in that format, and export a compressed copy only at the end for delivery. Always follow the format, length and naming rules of the station or desk receiving the file, and keep the original recording safely in case the story is challenged.