The term ("sound bite") is sometimes written incorrectly (or ironically) as "sound byte".
In film and broadcasting, a sound bite is a very short piece of a speech taken from a longer speech or an interview in which someone with authority or the average "man on the street" says something which is considered by those who edit the speech or interview to be the most important point.

http://en.wikipedia.org/wiki/Sound_byte

juga mengacu pada wikipedia, diterjemahkan sebagai cuplikan suara supaya menunjukkan bahwa yang dicuplik hanya suara, tak termasuk gambar

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Note added at 6 jam (2009-06-20 05:33:44 GMT)
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maksud saya berdurasi 30 detik

1. Sound bite is a very short piece of a speech taken from a longer speech or an interview in which someone with authority or the average "man on the street" says something which is considered by those who edit the speech or interview to be the most important point. (dalam http://en.wikipedia.org/wiki/Sound_byte)
2. Slogan singkat atau bagian kalimat yang diambil dari pidato dan diulang dalam media masa (dalam kamus Peter alim)
3. A sound bite is an audiolinguistic and social communications phenomenon whose nature was recognized in the late 20th century (dalam http://www.google.co.id/search?hl=id&defl=en&q=define:Sound ...

Result of Googling. Alternatively "Iklan yang berdurasi 30 detik"

By the way, as pointed out on Bahtera, the English expression has 'bite' not 'byte'.