Fix sample rate type annotations (#1789)

* Fix audio load sampling rate type

* Add backward-compatible sr cast and annotation

* Remove sr audio cast in audio load

* additional type annotation fixes on 1753

---------

Co-authored-by: tarepan <tarepan5884@gmail.com>

docs/glossary.rst

@@ -9,8 +9,8 @@ Glossary
         corresponds to amplitude of the waveform at sample `t`.
 
     sampling rate
-        The (positive integer) number of samples per second of a time series.  
-        This is denoted by an integer variable `sr`.
+        The number of samples per second of a time series.  
+        This is denoted by a positive number `sr`.
 
     frame
         A short slice of a :term:`time series` used for analysis purposes.  This

librosa/core/audio.py

@@ -63,7 +63,7 @@ def load(
     duration: Optional[float] = None,
     dtype: DTypeLike = np.float32,
     res_type: str = "soxr_hq",
-) -> Tuple[np.ndarray, float]:
+) -> Tuple[np.ndarray, Union[int, float]]:
     """Load an audio file as a floating point time series.
 
     Audio will be automatically resampled to the given rate

librosa/core/convert.py

@@ -600,14 +600,14 @@ def blocks_to_samples(
 
 @overload
 def blocks_to_time(
-    blocks: _IntLike_co, *, block_length: int, hop_length: int, sr: int
+    blocks: _IntLike_co, *, block_length: int, hop_length: int, sr: float
 ) -> np.floating[Any]:
     ...
 
 
 @overload
 def blocks_to_time(
-    blocks: _SequenceLike[_IntLike_co], *, block_length: int, hop_length: int, sr: int
+    blocks: _SequenceLike[_IntLike_co], *, block_length: int, hop_length: int, sr: float
 ) -> np.ndarray:
     ...
 
@@ -618,7 +618,7 @@ def blocks_to_time(
     *,
     block_length: int,
     hop_length: int,
-    sr: int,
+    sr: float,
 ) -> Union[np.floating[Any], np.ndarray]:
     ...
 
@@ -628,7 +628,7 @@ def blocks_to_time(
     *,
     block_length: int,
     hop_length: int,
-    sr: int,
+    sr: float,
 ) -> Union[np.floating[Any], np.ndarray]:
     """Convert block indices to time (in seconds)