Eric A. Dieckman

Benign exclusion of birds using acoustic parametric arrays

Excluding birds from areas can be important in aviation safety, agriculture, and facilities maintenance. Presenting audible stimuli or predator vocalizations in the affected area often has initial success, but has a limited effect over the long-term, even if the signals are varied to reduce the chances of the birds habituating to the sounds and objects. Many birds are highly vocal and rely on auditory communication in almost every aspect of their life history. By creating noise specifically targeted to be within the vocal range of the nuisance species we hypothesize that the birds will be less able to communicate and will move to more acoustically suitable environments. To avoid introducing noise pollution to the surrounding environment we create spatially well-controlled sonic nets using a mix of speakers and acoustic parametric arrays. To better understand the interaction of the sound field and the environment we combine finite difference solutions of the KZK equation with 3D acoustic finite integrati...

Reciprocal maximum‐length and related sequences in the generation of natural, spatial sounding reverberation.

The development of artificial reverberation has made considerable progress in recent years. In this research, a unique approach utilizing reciprocal maximum‐length sequences and related sequences is taken in generating a natural, spatial sounding reverberation. Additionally, an algorithm to shape and vary spaciousness within the context of an artificially generated reverberation is implemented. Results are verified through experimental measurements and subjective testing methods in a multichannel format. This work sheds light on alternative methods of generating artificial reverberation outside of commercially available systems. As a result, a direct application to room modeling techniques can be drawn with this work. Extensions of this research will comprise of investigations in objective and subjective behaviors of double‐sloped energy decays in acoustically coupled spaces. From an educational perspective, outcomes of this research can serve as a foundation in ear‐training for acoustics students seeking...

The importance of feature selection in supervised machine learning problems in acoustics

As machine learning processes begin to gain traction and are applied to problems in acoustics, there is a need to better understand the importance of all stages of the process. Here, we discuss the preprocessing stage, where features are extracted from raw data and the best features are chosen using algorithms such as linear discriminant analysis (LDA). This allows the creation of a small-dimensional, information-dense feature vector to be used in the machine learning process. Applications discussed include classification of ground vehicles based on their acoustic backscatter signature and classification of wall structures based on transmission loss measurements.

Robotics, free-reed instruments, and naughty birds: Finding the common thread

Musical acoustics often provides an accessible starting point for undergraduate research in which the basics are learned and applied to interesting problems. Even if students later study other areas of acoustics, the research experience gained is invaluable. This presentation will touch on a number of research projects encountered since the authors 2006 award for investigations of the acoustic behavior of Southeast Asian free-reed mouth organs. These projects come from a wide variety of acoustic disciplines, from nondestructive evaluation and architectural acoustics to benign bird exclusion and acoustic sensors for mobile robots, with the common thread of signal processing providing a focal point.

Use of pattern classification algorithms to interpret acoustic echolocation data from a walking-speed robotic sensor platform

An unresolved issue for autonomous walking-speed robots in unstructured outdoor environments is maintaining situational awareness. One strategy is combining information from different sensors so the robot can function in a variety of conditions and environments. The very low-cost Microsoft Kinect accessory incorporates active infrared and RGB video sensors to provide real-time depth information, as well as a 4-channel microphone array. We validate the Kinect sensors and investigate the combination of infrared (passive and active) and non-linear acoustic echolocation sensors on our mobile robotic sensor platform. By using an acoustic parametric array to generate the audible echolocation signal, a tightly-controlled beam of low-frequency sound can interrogate targets at long distances, while infrared imaging works well in the nearfield and in difficult weather conditions. Sophisticated signal processing techniques are required to combine and interpret the collected data; we present an example using pattern ...

Subsurface characterization of microelectronics using high‐frequency contact ultrasound.

The goal of this project was to develop and demonstrate a prototype system for characterizing subsurface features in microelectronic components using high‐frequency pulse‐echo ultrasound. Of particular interest are suspected counterfeit router components, which need to be inspected quickly and nondestructively with portable equipment that does not require extensive training to operate. Although ultrasound in the 100 MHz frequency range routinely images the relevant subsurface features in microelectronic components, scanning acoustic microscopes are neither portable nor inexpensive, and they require the component to be submerged in a bath of coupling water. Our alternative approach was a custom‐designed probe which uses direct contact with the component surface and does not employ water for coupling. Also, rather than high‐precision computer‐controlled scanning to produce images, the pulse‐echo waveforms are processed using our discrete wavelet fingerprinting algorithm. This maps out the subsurface layers ...

Measured and calculated sounding frequencies of pipes coupled with free reeds

The Asian free‐reed mouth organs incorporate approximately symmetric free reeds coupled to pipe resonators. Previous research has shown that the reeds in these instruments behave as “blown‐open” reeds in which the playing frequency is above both the natural frequency of the reed and the first peak of the measured impedance curve. Measurements of the input impedance have been made for a variety of these instruments. Detailed calculations of input impedance have also been made using transmission matrices, taking into account the position of the reed along the pipe, tuning slots, finger holes, and nonuniform cross sections. These calculations are in good agreement with the measured impedances of the same instruments. If the reed is treated as a damped, driven harmonic oscillator, the sounding frequencies of these reed‐pipes can be predicted using a phase relation between the reed vibration and the phase of the complex impedance. [Research supported by National Science Foundation REU Grant PHY‐0649007.]

Experimental and calculated frequencies of the Southeast Asian naw

The naw, an Asian free‐reed gourd pipe, is constructed of pipes open at both ends with a free reed in the side of each pipe near one end. The pipes of the naw are cylindrical over a significant portion of their length but have a slightly tapered bore near the reed end. The bottom end of the pipe can be covered with the player’s thumb to bend the pitch. Previous research on the khaen, a similar instrument with a cylindrical bore, found that the sounding frequencies of the khaen are well approximated using the simple equation for an open cylindrical pipe. This is not possible for the naw. A method of transmission matrices has been used to calculate the theoretical resonant frequencies of the naw pipes, both open and closed. The calculated values agree well with the resonant frequencies determined experimentally by measuring the input impedance of the pipe. When blown normally, the open pipe sounds near its calculated frequency, while the closed pipe sounds slightly lower than the open pipe frequency. By und...

Input impedance of asian free‐reed mouth organs

The khaen, naw, bawu, and sheng are examples of Asian free‐reed mouth organs, which incorporate free reeds coupled to pipe resonators. Previous research has shown that the reeds in these instruments behave as blown‐open reeds: the playing frequency is above both the natural frequency of the reed and the first peak of the measured impedance curve. Detailed calculations of input impedance have been made for a variety of these instruments, taking into account the position of the reed along the pipe, tuning slots, finger holes, and noncircular cross sections. The details of these calculations are in good agreement with the measured impedances of the same instruments, even in the higher harmonics. A study of the coupling of the free reed and pipe resonator has provided additional details about the influence of the pipe impedance on the playing frequency and sound spectrum of the reed‐pipe combination. [Research supported by NSF REU Grant PHY‐0354058.]