LENA’s norms for Words, Turns, and Vocalizations are based on 12-hour recordings; however, a family’s recording can be shorter, or can be up to 16 hours long. Variable durations make a direct comparison to the norms invalid. Statistical interpolation is necessary to compare variable length recordings to the norms and, by extension, to a family's own performance over time as the child ages. To this end, LENA computes and reports 12-hour projected values representing what the Words, Turns, and Vocalizations counts would have been had the recording been exactly 12 hours long. A recording must be at least 9.5 hours long to be eligible for this projection and comparison to the norms; shorter recordings are not valid for comparison. The 12-hour projected values are reported in:

• the roll-over information on the daily bars of the LENA report for recordings >9.5 hours
• the AWC, CTC, and CVC columns of the full recording export

The actual counts for Words, Turns, and Vocalizations in the processing results are just that - the actual number detected in the recording. The actual counts can be seen in:

• the hourly bars on the LENA reports
• the roll-over information on the daily bars of the LENA report for recordings <9.5 hours
• the AWC, CTC, and CVC columns in the hourly and 5-minute level exports
• the ITS file

To quickly find the actual counts for any recording, if desired, sum the hourly data. Note that the resulting values are not adjusted for duration and so are not appropriate for comparison against the 12-hour norms, nor against other recordings of varying durations from the same child or other children.