diff --git a/src/cryo_sbi/utils/image_utils.py b/src/cryo_sbi/utils/image_utils.py
index 4bab630..a4fa084 100644
--- a/src/cryo_sbi/utils/image_utils.py
+++ b/src/cryo_sbi/utils/image_utils.py
@@ -281,36 +281,68 @@ def __call__(self, image_path: str) -> torch.Tensor:
         return mrc_to_tensor(image_path)
 
 
-class WhitenImage:
+def estimate_noise_psd(images: torch.Tensor, image_size: int, mask_radius : Union[int, None] = None) -> torch.Tensor:
     """
-    Whiten an image by dividing by the noise PSD.
+    Estimates the power spectral density (PSD) of the noise in a set of images.
 
     Args:
-        noise_psd (torch.Tensor): Noise PSD of shape (n_pixels, n_pixels).
+        images (torch.Tensor): A tensor containing the input images. The shape of the tensor should be (N, H, W),
+                               where N is the number of images, H is the height, and W is the width.
+
+    Returns:
+        torch.Tensor: A tensor containing the estimated PSD of the noise. The shape of the tensor is (H, W), where H is the height
+                      and W is the width of the images.
+
     """
+    if mask_radius is  None:
+        mask_radius = image_size // 2
+    mask = circular_mask(image_size, mask_radius, inside=False)
+    denominator = mask.sum() * images.shape[0]
+    images_masked = images * mask
+    mean_est = images_masked.sum() / denominator
+    image_masked_fft = torch.fft.fft2(images_masked)
+    noise_psd_est = torch.sum(torch.abs(image_masked_fft)**2, dim=[0]) / denominator
+    noise_psd_est[image_size // 2, image_size // 2] -= mean_est
+
+    return noise_psd_est
+
 
-    def __init__(self, noise_psd: torch.Tensor) -> None:
-        self._noise_psd = noise_psd
+class WhitenImage:
+    """
+    Whiten an image by dividing by the square root of the noise PSD.
+    
+    Args:
+        image_size (int): Size of image in pixels.
+        mask_radius (int, optional): Radius of the mask. Defaults to None.
+    
+    """
+    
+    def __init__(self, image_size: int, mask_radius: Union[int, None] = None) -> None:
+        self.image_size = image_size
+        self.mask_radius = mask_radius
 
+    def _estimate_noise_psd(self, images: torch.Tensor) -> torch.Tensor:
+        """
+        Estimates the power spectral density (PSD) of the noise in a set of images.
+        """
+        noise_psd = estimate_noise_psd(images, self.image_size, self.mask_radius)
+        return noise_psd
+    
     def __call__(self, image: torch.Tensor) -> torch.Tensor:
         """
-        Whiten an image by dividing by the noise PSD.
-
+        Whiten an image by dividing by the square root of the noise PSD.
+        
         Args:
             image (torch.Tensor): Image of shape (n_pixels, n_pixels).
-
+        
         Returns:
-            reconstructed (torch.Tensor): Whiten image.
+            image (torch.Tensor): Whitened image.
         """
-
-        fft_image = torch.fft.fft2(image)
-        if image.ndim == 3:
-            fft_image = fft_image / torch.sqrt(self._noise_psd.unsqueeze(0))
-        elif image.ndim == 2:
-            fft_image = fft_image / torch.sqrt(self._noise_psd)
-        reconstructed = torch.fft.ifft2(fft_image).real
-
-        return reconstructed
+        noise_psd = self._estimate_noise_psd(image) ** -0.5
+        image_fft = torch.fft.fft2(image)
+        image_fft = image_fft * noise_psd
+        image = torch.fft.ifft2(image_fft).real
+        return image
 
 
 class MRCdataset: