Update noise.rs (#24)

* Update noise.rs

Add brown noise generator

* Use more readable clamp code

knyst/src/gen/noise.rs

@@ -6,7 +6,7 @@ use super::GenState;
 use crate as knyst;
 use crate::Sample;
 
-/// Whate noise (fastrand RNG based on wyrand)
+/// White noise (fastrand RNG based on wyrand)
 pub struct WhiteNoise {
     rng: fastrand::Rng,
 }
@@ -98,3 +98,39 @@ impl PinkNoise {
         GenState::Continue
     }
 }
+
+/// Brown noise (also known as red noise)
+///
+/// Brown noise is generated by integrating white noise.
+/// This implementation uses a simple integration of white noise samples with a small step size,
+/// and clamps the output to prevent it from exceeding the [-1.0, 1.0] range.
+pub struct BrownNoise {
+    rng: fastrand::Rng,
+    last_output: Sample,
+}
+
+#[impl_gen(range = normal)]
+impl BrownNoise {
+    #[allow(missing_docs)]
+    pub fn new() -> Self {
+        let mut rng = fastrand::Rng::new();
+        rng.seed(next_randomness_seed());
+        Self {
+            rng,
+            last_output: 0.0,
+        }
+    }
+
+    #[allow(missing_docs)]
+    pub fn process(&mut self, output: &mut [Sample]) -> GenState {
+        for out in output.iter_mut() {
+            let white = self.rng.f32() as Sample * 2.0 - 1.0;
+            // Adjust the coefficient to control the step size
+            self.last_output += white * 0.1;
+            // Clamp to [-1.0, 1.0] to prevent output from exceeding the range
+            self.last_output = self.last_output.clamp(-1.0, 1.0);
+            *out = self.last_output;
+        }
+        GenState::Continue
+    }
+}