This observational study involves ADHF patients at two sites in the United States and Germany. After informed consent and screening assessments, participants will perform daily voice recordings during their hospital stay, from admission until discharge. Alongside voice data, additional clinical information such as left ventricular ejection fraction, NTpro-BNP levels, and ECG-data will be collected for comprehensive analysis. The study's goal is to identify voice-based indicators of heart failure progression, with the potential to enhance remote monitoring and self-management strategies for heart failure patients.