In analogue systems, alignment level in broadcast chains is commonly 0 dBu (0.775 volts RMS) and in professional audio is commonly 0 VU (4 dBu, 1.228 volts RMS).
24-bit original or master recordings commonly have an alignment level at −24 dBFS to allow extra headroom, which can then be reduced to match the available headroom of the final medium by audio level compression.
FM broadcasts usually have only 9 dB of headroom, as recommended by the EBU, but digital broadcasts, which could operate with 18 dB of headroom, given their low noise floor even in difficult reception areas, currently operate in a state of confusion, with some transmitting at maximum level, while others operate at a much lower level, even though they carry material that has been compressed for compatibility with the lower dynamic range of FM transmissions.
[citation needed] In EBU documents[specify] alignment level defines −18 dBFS as the level of the alignment signal, a 1 kHz sine tone for analog applications and 997 Hz in digital applications.
Loudness normalisation to a fixed alignment level can improve the experience when listening to mixed material.