I think I should begin with a disclaimer that this article lays no pretence to scholarship. From William DuBay’s ‘Principles Of Readability’ and Jim Trelease’s ‘The New Read-aloud Handbook’, I have culled some information on listenability. We gain listening skills much before we learn to read. But as we move up from Grade 8, the difference between reading and listening skills decrease; at Grade 12, there is no difference between the two. And researchers have found that beyond Grade 12, it is easier to understand a text when read than when listened to.
The Reading Grade (RG) is measured on a scale of 1 to 17+. Let the scale for Listening Grade (LG) be 1 to 12+. I assume that there is a gradual and uniform decline in listening skills with LG = 0 and RG = 3 as starting points. I assume that if LG increases by 1, then RG increases by 0.75. Put the other way, if RG increases by 1, then LG increases by 1.33. This assumption ensures that at Grade 12, LG = RG. If this assumption is right, then here are my conversion formulae:
LG = (4/3) * (RG – 3)
RG = [(3/4) * LG] + 3
Since books are graded based on RG, it becomes easy for us to calculate LG. Suppose you pick up a Grade 7 book and wish to know its listenability. In this case, RG = 7 and hence LG = (4/3) * (7 – 3) = (4/3) * (4) = 16/3 = 5.33. The score tells us that the book may be read aloud to a fifth grader.
But what if the book’s grade is not known? We may use Harry McLaughlin’s Smog Grading for readability and Irving Fang’s Easy Listening Formula (ELF) for listenability. But to keep our calculations simple, I prescribe modified versions of these formulae.
Modified Smog Reading Grade (MSRG) = 3 * [(square root of P3) + 1], where P3 is the number of polysyllabic words in three sentences.
Substituting the MSRG in the conversion formula for LG, we get Modified Smog Listening Grade (MSLG) = 4 * (square root of P3).
Fang’s ELF is calculated by counting the number of syllables more than one per word in a sentence. ELF = S – W, where S and W are the number of syllables and words in a sentence respectively. This formula punishes every extra syllable. Now, if we assume that all polysyllables are equally difficult, then we get the Approximate Easy Listening Grade (AELG) = N + P, where N and P are the number of non-monosyllabic words and polysyllabic words in a sentence respectively.
I think I should end with a caution that these formulae are yet to be thoroughly tested.