Hark! The Herald Angels Sing

Posted on: 27 December 2020

When we think of Christmas music, the first thing that springs to mind is the tireless onslaught of Christmas hits that play on loop while we desperately do our last-minute gift shopping. A more enticing association is that of a choir mesmerising us with traditional Christmas songs that seem to take us back to our school days, or to concerts we’ve attended in frosty churches late at night. We may even conjure up the image of a choir of angelic-sounding children intoning versions of O Come All Ye Faithful, The First Noel or Wexford Carol. But what is it that makes children’s voices sound so angelic?

It all starts at birth. When children are born, their throats are not yet fully developed and the range of sounds they can produce are quite limited, which is what we think of as a baby cooing or babbling. Inside the voicebox, the vocal cords are very short (about 2.5mm) and capable of producing only very high-pitched sounds, which is why a baby’s cry seems to pierce our ears! As children get older, their throats grow and their vocal folds lengthen. This allows them to sing at the sweet, high notes that we enjoy during our Christmas carols. Both boys and girls are capable of producing much the same notes, which also allows them to sing in unison.

Things change at puberty however, when the vocal cords reach adult length: up to 15mm for females and up to 21mm for males. Boys develop a recognisably deeper pitch, but even girls see a small drop in pitch too. Where children were able to sing in unison, we now see a segregation in choirs, where those with a high pitch tend to be in the soprano or alto range, while those with a deeper pitch are usually tenor or bass. Such choirs are no less enjoyable to listen to – just different!

This article was written by Dr. Ciarán Kenny, Assistant Professor, Department of Clinical Speech and Language Studies, Trinity College Dublin

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