Purpose of cascade buffers
The RC dividers (4.7kΩ and 100 nF, 1kΩ and 10 nF) are filters, with shoulder frequencies of 1/(2πRC) each, giving you two 1-pole low-pass filters cascaded into a 2-pole LPF. They're buffered so that each filter doesn't load the prior stage. The resistor divider out front sets the gain.