Population or TSA (Total Survey Area):

Official broadcast area of radio station, used as a basis for audience measurement. A station’s signal can often be heard well beyond this boundary, but the further away it gets, the smaller the audience becomes. Hence, a smaller TSA gives the station a better percentage reach.


The number of different people within the target audience who will hear at least one advertisement from a campaign. Expressed in thousands or as a percentage.

Impacts (Reach x Frequency):

The total number of exposures to a schedule of advertisements. Not a measure of the number of different people exposed to a commercial.

Frequency or OTH (Opportunities to Hear):

The average number of times the audience reached by an advertising schedule is exposed to a commercial. For a successful campaign, a rule of thumb is to achieve at least 4 OTH in the first week. Naturally, the more times an ad is heard, the better the result.

Total Hours:

The total amount of listening by all listeners to a station (or group of stations) at some point during a week, expressed in thousands or as a percentage of the population in the TSA.

RAJAR (Radio Joint Audience Research):

An independent research body who monitor the performance of all radio stations in the UK, whether BBC or commercial. Results for most stations are issued on a quarterly basis.


Are the correlation between Impacts and Population, it is not used so much now but was originally used when people bought on an impact basis. To find out the Ratings you divide the impacts by the population then multiply by 100.

Cost Efficiency:

Cost efficiency is another way of determining how much wastage a station generates (or not as the case may be). The figure is similar to a cost per thousand but it assumes all stations are based on 2.00 so is used as a comparative tool rather than a buying tool. The closer the figure to the base of 2.00 the better.