You are presented with multiple paper abstracts, alongside the associated literature review and chapter titles. Given the provided information, you are going to do a literature review. Please generate a coherent literature review that synthesizes the content, draws connections between different works, highlights major findings, and identifies any gaps in the existing research.

Literature Review Title: A SURVEY OF AUDIO PROCESSING ALGORITHMS FOR DIGITAL STETHOSCOPES 
Chapter Title:  INTRODUCTION 
1. Abstract of Cited Paper (BIB001):  The objective of the present paper is to provide a detailed review of the most recent developments in instrumentation and signal processing of digital phonocardiography and heart auscultation. After a short introduction, the paper presents a brief history of heart auscultation and phonocardiography, which is followed by a summary of the basic theories and controversies regarding the genesis of the heart sounds. The application of spectral analysis and the potential of new time-frequency representations and cardiac acoustic mapping to resolve the controversies and better understand the genesis and transmission of heart sounds and murmurs within the heart-thorax acoustic system are reviewed. The most recent developments in the application of linear predictive coding, spectral analysis, time-frequency representation techniques, and pattern recognition for the detection and follow-up of native and prosthetic valve degeneration and dysfunction are also presented in detail. New areas of research and clinical applications and areas of potential future developments are then highlighted. The final section is a discussion about a multidegree of freedom theory on the origin of the heart sounds and murmurs, which is completed by the authors' conclusion.

Literature Review:
Auscultation is one of the oldest, cheapest and most useful techniques for the diagnosis of heart disease. Since their invention in 1816, stethoscopes have been used as part of the initial evaluation of all patients with suspected heart or lung problems. An experienced physician can diagnose a large number of clinical conditions just from the initial auscultation of the patient's chest BIB001 . There have been several attempts to create electronically enhanced stethoscopes, with better sound amplification and frequency response. However, and according to BIB002 , their introduction into clinical practice has been hindered by factors such as their background noise, unfamiliar sounds to clinicians due to filtering or fragility and bad ergonomic design. Recent advances in electronics and digital circuits allow us to not only overcome these problems but also to exploit the benefits of digital signal processing for signal analysis and visualization. In this paper we will embrace this novel perspective and analyze the state-of-the-art in audio processing of heart sounds that might be adequate for integrating into this next generation of stethoscopes. A deeper explanation of digital stethoscopes is given in Section 2, a review of audio processing methods is described in Section 3, followed by a discussion (Section 4) on the future of digital stethoscopes and how biomedical engineers can contribute to the success of this technology.