This chapter discusses the acoustic testing of wood in finished wooden musical instruments, emphasizing the multifaceted nature of what constitutes a good sound. The chapter highlights that achieving a desirable sound involves a combination of resonance, clarity, and other factors that go beyond personal taste. While advanced technologies discussed in earlier chapters might not be universally available, this chapter argues for the necessity of accessible acoustic evaluation facilities for all luthiers. The chapter outlines the key acoustic parameters that define the sound of wood in a stringed instrument, including resonance, richness, clarity, and definition. Resonance refers to the instrument’s ability to sustain sound, while richness relates to the complexity of the sound’s frequency response. Clarity and definition pertain to how distinct each note is and the balance and flexibility of the instrument’s sound. The chapter also discusses the influence of traditional designs, player preferences, and the importance of removing unwanted resonances from the instrument’s sound. It emphasizes that a good instrument results from the careful integration of design, materials, construction, and an understanding of acoustic physics. Furthermore, the chapter details the use of software and instrumentation in sound analysis, highlighting the importance of tools like FFT (Fast Fourier Transform) and unidirectional microphones. These tools enable luthiers to measure and analyze the acoustic properties of instruments with adequate precision. Finally, the chapter provides methodologies for analyzing the frequency response of instruments, including tap tests for the tonewood mounted as the top plate and back of the bowl of an instrument. These tests help luthiers identify and address acoustic issues in their instruments.