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CHECKLISTS AND SONOGRAMS
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How to interpret a Sonogram (Afrikaans)
A sonogram provides a visual representation of the call of a bird, and it often provides a more meaningful rendition of the sound than when the call is put into words. The sonogram is a graph with horizontal and vertical axes, and the individual parts of the bird's call appear on the graph as lines, dots, streaks, etc. The vertical axis measures frequency, so the point at which a dot or streak appears against this axis indicates how high- or low-pitched the sound is. An owl's hoot, for example, will lie close to the base of the graph, whereas a sunbird's very high-pitched song will lie close to the top of the graph. Pitch is measured in kiloHertz (kHz) and for most birds the uppermost point of the scale, is at 7 or 8 kHz (although some birds can sing up to 15 kHz). The horizontal axis tracks the sound over time. The intensity, shape and size of the sound bites on the graph reflect the loudness of the call, how long each note lasts, whether each remains at a constant pitch or whether the sound rises or falls. The examples below show how three very different calls are rendered on sonograms. (click on the image to view/download the sonogram)
The call of the Rufous-cheeked Nightjar is low-pitched (between 1-3 kHz) and starts with two (or more) pairs of loud, sharp notes uttered at half-second intervals - this is the 'chu koo' part of the call. The call then changes to a sustained low-pitched churring song that is actually made up of 30-35 individual rapid notes/second. Only 2 or 3 seconds of this 'churr' are shown on the sonogram, but the call can continue for a minute or more. Whenever a sonogram has closely spaced vertical lines you know that the call is a churring sound of some kind, and if these are high-pitched, as in the Wailing and Grey-backed cisticolas' calls, the churring would probably be described as a trilling. The Neddicky utters a monotonous clicking note from a treetop and may continue for many seconds, and even for minutes on end. The sonogram shows only about a 5-second burst of such a call. Here you can see that the notes are pitched at about 3 kHz and that they are uttered at evenly spaced intervals of 3-4 notes/second. The similarity of each note and the uniformity in their spacing gives the call its monotonous refrain, and in this particular sound recording there is a double-element to each note that gives the notes an element of slur.
The sonogram for the Levaillant's Cisticola's song shows that this call is much more varied in pitch than those of the nightjar and Neddicky. The whole song lasts for about 1 second, starting with a single note, higher-pitched than the others; this followed by a warble that descends and then rises in pitch. It is rendered in words as 'tsi, tsiororee' and the value of the sonogram is in showing that the call, unlike those of many other cisticolas, is not particularly high-pitched, and that it descends in pitch in the middle ('oro') and rises again at the end ('ree').
Afrikaans: Hoe om 'n sonogram te vertolk
'n Sonogram is 'n visuele voorstelling van 'n voël se roep en is dikwels 'n meer betekenisvolle weergawe as die een wat in woorde gegee word. Die sonogram is 'n grafiek met horisontale en vertikale asse, stippels, strepe, ens. Die vertikale as meet frekwensie, en hoe hoog 'n stippel of streep op hierdie as lê, sê vir jou hoe hoog - of hoe laag - die toonhoogte is. 'n Uil se gehoe sal byvoorbeeld naby die grafiek se basis lê, terwyl 'n suikerbekkie se baie hoë sang naby die grafiek se bopunt lê. Toonhoogte word in kilohertz (kHz) gemeet en vir die meeste voëls is die boonste punt van die skaal op 7 of 8 kHz (maar sommige voëls tot kan tot 15 kHz hoog sing). Die horisontale as gee die klank oor 'n tydsverloop weer. Die intensiteit, vorm en grootte van die klankdeeltjies op die grafiek stel voor hoe hard die roep is, hoe lank elke noot duur, of elkeen op 'n konstante toonhoogte bly en of die klank styg of daal.
Die voorbeelde hier toon hoe drie baie verskillende roepe deur sonogramme weergegee word. In die eerste, die Rooiwangnaguil s'n, het die roep 'n lae toonhoogte (tussen 1-3 kHz) en begin dit met twee (of meer) pare luide, skerp note, met tussenposes van 'n halfsekonde geuiter - dit is die 'tjukoe'-gedeelte van die roep. Die roep verander dan na 'n volgehoue lae tjur-sang wat eintlik uit 30-35 afsonderlike, baie vinnige note/sekonde bestaan. Net 2 of 3 sekondes van hierdie 'tjurr' word op die sonogram gewys, maar die roep kan 'n minuut of langer aanhou. Wanneer 'n sonogram se vertikale lyne baie na aan mekaar lê, weet jy die roep is die een of ander tjurgeluid, en as hulle op 'n hoë toonhoogte is, soos die Huil- en Grysrugtinktinkie s'n, sal die getjur waarskynlik as 'n trilgeluid beskryf word.
Die Neddikkie uiter 'n eentonige kliknoot van 'n boomtop af wat sekondes, of selfs minute lank kan aanhou. Die sonogram wys net ongeveer 5 sekondes van so 'n roep. Hier kan jy sien dat die note op 'n toonhoogte van ongeveer 3 kHz is en dat hulle met gereelde tussenposes van ongeveer 3-4 note/sekonde geuiter word. Die eendersheid van elke noot en die eweredige spasiëring gee die roep sy eentonige refrein en in hierdie besondere klankopname is daar 'n dubbele element tot elke noot wat die note 'diktongig' laat klink.
Die sonogram van die Vleitinktinkie se sang toon dat hierdie roep se toonhoogte baie meer wissel as die naguil en Neddikkie s'n. Die hele sang duur ongeveer 1 sekonde en begin met 'n enkele noot, op 'n hoër toonhoogte as die ander, gevolg deur 'n gekweel waarvan die toonhoogte daal en dan styg. In woorde word dit as 'tsi, tsiororiee' weergegee en die nut van die sonogram is om te toon dat die roep, anders as dié van ander tinktinkies, nie besonder hoog is nie en dat die toonhoogte in die middel ('oro') daal en dan aan die einde ('riee') weer styg.
Sonograms provided by www.simplybirding.com
© 2015 Penguin Random House South Africa