Agnieszka Roginska

BSoniq: A 3-D EEG Sound Installation

This paper presents “BSoniq”, a 3-D EEG sound installation, in which, the user can perceive spatial characteristics of EEG signals in a multi-channel environment. With this installation, the users (listeners) wear a wireless EEG headset and listen to sounds generated in real-time from their brain waves to perceive brain activities which they may not be aware of in their daily life. To accomplish a brain electrical activity sonification, brainwave source localization features of multichannel EEG are converted into sound images. These allow for simple interpretation, because of their spatial temporal differences. Signals recorded from the scalp are “decoded” from the multi-channel EEG, by applying filters and modulation to the EEG signal with an audio file. The main goal is to use sound to render the original data in a suitably transformed way so that we can invoke our natural pattern recognition capabilities to search for regularities and structures. Brainwave sonification is also very practical in brain-computer interface (BCI) user feedback design. Deciding how the control of parameters, processing and filtering of inaudible data are used is important in this process. Using listening as a tool serves both as an aesthetic and/or scientific purpose. The human hearing system is able to decode and interpret complex auditory scenes. The more structured the representation of the sonified data, the better the accessibility and intelligibility of the chosen process [9].

A novel sonification approach to support the diagnosis of Alzheimer's dementia

Alzheimer’s disease is the most common neurodegenerative form of dementia that steadily worsens and eventually leads to death. Its set of symptoms include loss of cognitive function and memory decline. Structural and functional imaging methods such as CT, MRI, and PET scans play an essential role in the diagnosis process, being able to identify specific areas of cerebral damages. While the accuracy of these imaging techniques increases over time, the severity assessment of dementia remains challenging and susceptible to cognitive and perceptual errors due to intra-reader variability among physicians. Doctors have not agreed upon standardized measurement of cell loss used to specifically diagnose dementia among individuals. These limitations have led researchers to look for supportive diagnosis tools to enhance the spectrum of diseases characteristics and peculiarities. Here is presented a supportive auditory tool to aid in diagnosing patients with different levels of Alzheimer’s. This tool introduces an audible parameter mapped upon three different brain’s lobes. The motivating force behind this supportive auditory technique arise from the fact that AD is distinguished by a decrease of the metabolic activity (hypometabolism) in the parietal and temporal lobes of the brain. The diagnosis is then performed by comparing metabolic activity of the affected lobes to the metabolic activity of other lobes that are not generally affected by AD (i.e., sensorimotor cortex). Results from the diagnosis process compared with the ground truth show that physicians were able to categorize different levels of AD using the sonification generated in this study with higher accuracy than using a standard diagnosis procedure, based on the visualization alone.

Electric guitar—From measurement arrays to recording studio microphones

A joint research effort by the audio recording programs at the University of Massachusetts Lowell and New York University has made use of a 32-microphone measurement array in the quantification and visualization of the spectral radiation of musical instruments. Work to date has focused on electric guitar and piano. The measured directivities of the guitar amplifiers offer rich insight for the recording engineer. Traditional microphone selection and placement strategies formed over decades, before such data existed, are found to have merit. The data also shed light on those potentially unattractive microphone locations to be avoided. The measurements, taken with high spatial resolution, reveal a process for microphone placement as much as providing a window into showing exactly where to place them. Measurements of the acoustic radiation from electric guitar amplifiers reveal a spatial complexity that many recording engineers anticipate, and add valuable further insight.

High resolution radiation pattern measurements of a grand piano - The effect of attack velocity

The sound radiation pattern of a grand piano is highly complex and depends on the shape of the soundboard, construction of the frame, reflections from the lid, and other parts of the instrument’s structure. The spectral energy generated by and emitted from the instrument is further complicated by the sound production mechanism (hammers, strings), the attack velocity, and results in independently complex behaviors depending on the register of the piano. This paper presents the acoustic measurements of the radiation pattern of a grand piano using a high spatial resolution measurement technique. Measurements of a Yamaha Diskclavier were taken using a 32-channel microphone array with a 2-in. spacing between capsules. The complex radiation patterns and overtone structure is analyzed for middle-C at three attack velocities—pianissimo, mezzo forte, and forte. Comparisons of the effect of attack strength on frequency response and radiation pattern are presented.

Electric guitar—A blank canvas for timbre and tone

The electric guitar is a complex mechanical, electrical, and acoustic system, invented less than a century ago. While more traditional instruments such as voices and violins, trumpets and tympani, piano and piccolo might possess innate traits that most listeners easily identify, the electric guitar is a sound synthesizer capable of a vast range of sounds. The guitar, the amp, and the recording techniques used enable the performer and the engineer to define and refine elements of tone, almost without limit. Electric guitar has no single reference tone quality, but instead invites, and even inspires performers and recordists to create new sounds and explore alternative timbres as desired.

The maximum intelligible range of the unamplified human voice

The Anglican preacher George Whitefield preached to some of the largest reported crowds in recent history during the Methodist revivals in 18th century London. Benjamin Franklin later performed an auditory experiment in Philadelphia from which he estimated Whitefield could be heard by 30,000 listeners at once. Using the data from Franklin’s experiment and acoustic model of colonial Philadelphia, Whitefield’s on-axis averaged sound pressure level at one meter has been calculated to be about 90 dBA, consistent with the loudest values measured from trained vocalists today. Using period maps and topological data, acoustic models have been constructed of the sites of Whitefield’s largest crowds in London, using a human voice source with the projected SPL for Whitefield’s preaching voice. Based on the total audience area whose speech transmission index value is greater than that at Franklin’s position in the Philadelphia experiment, the total intelligible audience area can be calculated. Using Franklin’s own cr...

Sound radiation of trained vocalizers

Current research at NYU has focused on the maximum crowd size that could hear a single unamplified voice, including the impact of vocal directivity. Most literature on the radiation of the spoken voice has focused on the context of conversation in workspaces and thus has not investigated oratorical speech at high levels. Trained actors and singers, however, employ more methods of projection than are used in conversational speech and can achieve higher loudness as well. The radiation patterns from these types of communication have not been quantifiably studied yet. This paper investigates the horizontal plane radiation patterns of different methods of projection in trained vocalizers using relative intensity levels at 60 cm from the front of the speaker. In general, the method of production is not found to have a strong effect on the horizontal plane directivity.

Computer simulation of Benjamin Franklin's acoustic experiment on George Whitefield's oratory

The Anglican preacher George Whitefield was renowned for his loud voice and the huge crowds he drew during the transatlantic revivals of the 18th century. Benjamin Franklin was skeptical of the accounts of crowds of 30,000 gathering in London, and when Whitefield came to Philadelphia in 1739, Franklin performed one of the earliest recorded ‘archeoacoustic’ experiments: walking backwards down Market Street, Franklin continued listening to Whitefield speak from the old courthouse until his sermon became unintelligible. Using this maximum intelligible distance, Franklin calculated that Whitefield probably could have been heard by more than 30,000 listeners. Using Franklin’s account and period maps and prints of the colonial city, we have built a virtual CAD model of Philadelphia as it would have existed during Whitefield’s visit. This paper discusses techniques employed using geometric acoustic simulation software to approximate the loudness of Whitefield’s voice based on the STI at Franklin’s position. To d...

Spatial variability of timbre for an electric guitar amplifier

Impulse response measurements of an electric guitar amplifier at high spatial resolution reveal frequency response variabilities likely to drive key elements of timbre for the recording engineer. Data collection from the very near field of the driver to a distance of several feet away, gathered in a three-dimensional grid around the open-backed, single-driver, Fender Deluxe electric guitar amplifier quantify the variations in frequency response which may be exploited by the recording engineer using microphone placement to influence timbre.

A measurement technique achieving high spatial resolution for sound sources within a performance venue

A proof of concept for gathering high spatial resolution sound radiation, from near field to far field, in 3 dimensions around an electric guitar amplifier is presented, with an eye and ear toward applying a similar technique to other essential sound sources. A high density microphone array is used to gather many thousands of impulse response in a hemi-anechoic space. The resulting data serves as a useful input to room models and auralizers, but finds added purpose as an educational tool in musical acoustics and sound recording.