Classification system for classifying an external impact on a window or on an access opening of an enclosed structure, the classification system comprising: a microphone configured for producing an audio signal (AS) corresponding to a sound within the enclosed structure; a barometric pressure sensor configured for producing a pressure signal (PS) corresponding to an air pressure within the enclosed structure; an audio signal pre-processor configured for deriving a pre-processed audio signal (PAS) from the audio signal (AS); a pressure signal pre-processor configured for deriving a pre-processed pressure signal (PPS) from the pressure signal (PS); an audio signal feature processor configured for extracting audio features from the pre-processed audio signal (PAS) in order to produce an audio feature vector (AFV), wherein the audio features are characteristic for the audio signal (AS) and the audio feature vector (AFV) comprises values of the audio features; an pressure signal feature processor configured for extracting pressure features from the pre-processed pressure signal (PPS) in order to produce a pressure feature vector (PFV), wherein the pressure features are characteristic for the pressure signal and the pressure feature vector (PFV) comprises values of the pressure features; a feature combining processor configured for combining the audio feature vector (AFV) and the pressure feature vector (PVF) in order to produce an audio feature and pressure feature vector (APV); and a classification processor configured for classifying the external impact on the window or the access opening by classifying the audio feature and pressure feature vector (APV) in order to produce a classification output (CO); wherein the classification processor is configured for executing a first machine learning algorithm, wherein the audio feature and pressure feature vector (APV) is fed to an input layer of the first machine learning algorithm, and wherein the classification output (CO) is based on an output of the first machine learning algorithm. a microphone configured for producing an audio signal (AS) corresponding to a sound within the enclosed structure; a barometric pressure sensor configured for producing a pressure signal (PS) corresponding to an air pressure within the enclosed structure; an audio signal pre-processor configured for deriving a pre-processed audio signal (PAS) from the audio signal (AS); a pressure signal pre-processor configured for deriving a pre-processed pressure signal (PPS) from the pressure signal (PS); an audio signal feature processor configured for extracting audio features from the pre-processed audio signal (PAS) in order to produce an audio feature vector (AFV), wherein the audio features are characteristic for the audio signal (AS) and the audio feature vector (AFV) comprises values of the audio features; an pressure signal feature processor configured for extracting pressure features from the pre-processed pressure signal (PPS) in order to produce a pressure feature vector (PFV), wherein the pressure features are characteristic for the pressure signal and the pressure feature vector (PFV) comprises values of the pressure features; a feature combining processor configured for combining the audio feature vector (AFV) and the pressure feature vector (PVF) in order to produce an audio feature and pressure feature vector (APV); and a classification processor configured for classifying the external impact on the window or the access opening by classifying the audio feature and pressure feature vector (APV) in order to produce a classification output (CO); wherein the classification processor is configured for executing a first machine learning algorithm, wherein the audio feature and pressure feature vector (APV) is fed to an input layer of the first machine learning algorithm, and wherein the classification output (CO) is based on an output of the first machine learning algorithm. <EOS>