A lock-in amplifier is used to determine the acoustic response a system over a range of stimulus frequencies. The lock-in amplifier implements this by simultaneously creating a stimulus at a selected frequency, recording the resulting response, and isolating the part of the signal that is produced at the incident frequency. This gives information about the resonant frequencies of the analyzed system, which is useful for determining the system’s acoustic properties. For this particular project, we will be using the lock-in amplifier to measure the resonance frequencies of open tubes of various lengths. Additionally, tube-like systems such as corrugated tubes, tubes connected in T-joints, and tubes partially submerged in water can be analyzed using this technique. A better understanding of the acoustic properties of these systems is useful because they are similar to several real world systems such as heart stents and oil pipelines.
This work studies how the speed of sound in a corrugated tube decreases relative to the speed in free space. Previous students at the University of North Carolina Asheville have engaged in research to determine this speed. The results from these studies were obtained with an uncertainty that rendered the changes of speed within the tube indeterminable due to low sampling rate. Other experimenters have published similar experiments under the assumption that the change in the speed of sound remains constant throughout the tube. This study seeks to refine previous research by measuring possible variations in the speed along the tube’s length. To accomplish this, a higher sampling rate and noise reduction procedures will be used to lower uncertainty, thereby allowing the accuracy necessary to map the change of the speed of sound as it travels through the tube. This will be done by using a ‘one-shot’ method in which frequency controlled bursts of sound are received by a decreasingly distant sound sensor.
This work studies how the speed of sound in a corrugated tube decreases relative to the speed in free space. Previous students at the University of North Carolina Asheville have engaged in research to determine this speed. The results from these studies were obtained with an uncertainty that rendered the changes of speed within the tube undeterminable due to low sampling rate. This study seeks to refine previous research by measuring possible variations in the speed along the tube’s length. To accomplish this, a higher sampling rate and noise reduction procedures will be used to lower uncertainty, thereby allowing the accuracy necessary to map the change of the speed of sound as it travels through the tube. This will be done by using a ‘one-shot’ method in which frequency controlled bursts of sound are received by a decreasingly distant sound sensor. Additional analysis will be done to investigate the effects of dispersion. This will be done by analyzing pulses of different frequencies as well as doing some frequency spectrum analysis.
