Add a Hann function for the STFT helper

src/util.rs

@@ -1,6 +1,7 @@
 //! General conversion functions and utilities.
 
 mod stft;
+pub mod window;
 
 pub use stft::StftHelper;
 

src/util/window.rs

@@ -0,0 +1,17 @@
+//! Windowing functions, useful in conjuction with [`StftHelper`][super::StftHelper].
+
+use std::f32;
+
+/// A Hann window function.
+///
+/// <https://en.wikipedia.org/wiki/Hann_function>
+pub fn hann(size: usize) -> Vec<f32> {
+    // We want to scale `[0, size]` to `[0, pi]`.
+    let scale = (size as f32 - 1.0).recip() * f32::consts::PI;
+    (0..size)
+        .map(|i| {
+            let sin = (i as f32 * scale).sin();
+            sin * sin
+        })
+        .collect()
+}