## 2 Manufacturing Processes of Musical Instruments Made of Composites and Alternative Materials
### Experimental and Numerical Methods for Musical Instrument Vibroacoustic Studies
#### 3.1.1 Vibro-Acoustic Assessments of Musical Instruments with Composites  
The type of matrix and reinforcement significantly impact the material's mechanical and acoustic properties. The arrangement and thickness of composite layers influence their bending and vibrational characteristics, which, in turn, affect the acoustic response [74]. The damping capacity of the material plays a role in absorbing and dissipating vibrational energy. The manufacturing method used to produce the composite, such as lay-up technique, curing conditions, and molding processes, can affect material uniformity and, consequently, vibro-acoustic properties. Moreover, the overall design and geometry of the composite structure can influence its dynamic response and acoustic performance. The exploration of composite materials in the manufacturing of musical instruments constitutes an intriguing research domain within musical acoustics, steadily gaining prominence over time. In an in-depth examination focused on violins, [PERSON] [75] delineated prerequisites essential for replicating the vibrational characteristics of a wooden plate using a plate made from a different material. Building upon these criteria, [PERSON], and [PERSON] [76]delved into the prospect of substituting wood with a composite plate, particularly in the crafting of top plates for guitars and violins. The violin stands as one of the most extensively studied musical instruments. [PERSON] et al. [60] dedicated their research to establish a measurement protocol for potential modal analysis evaluations of wooden violins. In their investigation, both a carbon and a wooden violin were subjected to testing. The measurements primarily focused on coherence, the occurrence frequency of signature modes, their damping characteristics, and the associated risk factors linked to each measurement method. In the latter case, the FRF was computed for various inputs and outputs. The violins were excited using an impact hammer, an electromagnetic shaker, a piezoelectric element, and a loudspeaker, while the response was captured through the utilization of an accelerometer and a laser scanning vibrometer. Moreover, [PERSON] et al. [12] performed listener experiments for the evaluation of violins made of composites. Soundboards made of various composites were attached to a violin body, in a way that the only difference among the violins was the soundboard. Part of the study was the measurement of the acoustic radiation of the violins in a heminenchoic room with an impact hammer excitation. The variation in the radiation is shown in Figure 6. The study concluded that diverse sounds and timbres of violins made from fiber-reinforced polymers can be produced. [PERSON] et al. [13] discussed about the performance of violins made from carbon fiber composites and wooden ones, using finite element modal analysis for their comparison. The models underwent validation through comparisons with experimental studies conducted by other researchers, leading to the conclusion that, for instruments sharing identical geometry, a superiority of wood over CFRP was evident. [PERSON] and [PERSON] [77] presented the development of a carbon fiber violin. During the manufacturing process, they performed modal analysis in the frequency domain using laser vibrometer measurements. Furthermore, the investigations conducted by [PERSON] [71] and [PERSON] et al. [72] using FEM simulations delved into the feasibility of replacing the conventional wood material in top plates with composite materials. The outcomes of both studies revealed a noteworthy distinction in the vibrational characteristics between composite soundboards and their traditional wooden counterparts. [PERSON] et al. [63] employed a bio-based composite material for the violin top plate in their study, wherein they conducted an analysis to determine its elastic and damping properties through the application of an inverse method. This involved a synergistic approach that combined modal finite element analysis and experimental modal measurements.