Four tones can be heard. The first is a squeeling of discomfort. You may ignore this.
The next three sounds are the infamous sounds phoneticly discribed by
(page 5 in "Uber das verhalten des Haussperlings"), with "krüü".
They form the highest alert a sparrow colony can sound.
It is normally used in a larger colony when a sparrowhawk is first seen aproaching.
In this case though it is uttered quite calm.
This is because every house sparrow is allready in hiding from a previous threat.