Concatenate instead of add in vggish_train_demo.py.

Also added 'sudo' to installation instructions.

research/audioset/README.md

@@ -84,14 +84,15 @@ Here's a sample installation and test session:
 #   $ source vggish/bin/activate  # Assuming you use bash
 # Leave the virtual environment at the end of the session by running
 #   $ deactivate
+# Within the virtual environment, do not use 'sudo'.
 
 # Upgrade pip first.
-$ python -m pip install --upgrade pip
+$ sudo python -m pip install --upgrade pip
 
 # Install dependences. Resampy needs to be installed after NumPy and SciPy
 # are already installed.
-$ pip install numpy scipy
-$ pip install resampy tensorflow six
+$ sudo pip install numpy scipy
+$ sudo pip install resampy tensorflow six
 
 # Clone TensorFlow models repo into a 'models' directory.
 $ git clone https://github.com/tensorflow/models.git

research/audioset/vggish_train_demo.py

@@ -114,8 +114,8 @@ def _get_examples_batch():
   noise_labels = np.array([[0, 0, 1]] * noise_examples.shape[0])
 
   # Shuffle (example, label) pairs across all classes.
-  all_examples = sine_examples + const_examples + noise_examples
-  all_labels = sine_labels + const_labels + noise_labels
+  all_examples = np.concatenate((sine_examples, const_examples, noise_examples))
+  all_labels = np.concatenate((sine_labels, const_labels, noise_labels))
   labeled_examples = list(zip(all_examples, all_labels))
   shuffle(labeled_examples)