Abstract:

Human speech signals produce sound waves that induce vibrations on objects that they encounter. Such vibrations can be measured via laser vibrometers and possibly used in speech eavesdropping attacks. However, there is still much to learn about when this attack is feasible. In this paper, we aim to broaden our understanding of the viability of laser eavesdropping attacks to compromise speech in the commercial user space. In our study, we design experiments to measure the subtle vibrations induced on commonly-available objects by nearby speech, using commercially sold, high-precision laser vibrometers. To observe idealized success rates of the attack, we maintain certain physical parameters in favorable conditions that represent best case scenarios for an attacker. We test three primary attack scenarios considering different relative positions to the target object. Additionally, we consider many important experimental parameters to understand the generalizability of the attack, including: speech sources, loudness levels, vibration propagation media, and object materials.

Our vibrometer recorded signals were analyzed via a two-pronged methodology including, (1) time domain, frequency spectrum, cross correlation, and speech intelligibility metric analyses and (2) an information extraction analysis using both human listeners and automated recognition tools. Our results suggest that eavesdropping attacks using a laser vibrometer may be practical in some situations and parameter settings (i.e., intelligence missions). However, we find that live aerial human speech and machine-rendered speech at a normal conversational loudness level does not show signs of significant leakage in our analysis.

Paper Download: The final version of the paper can be downloaded here.

Data Download: The full set of our collected data can be downloaded here.

* The files include the vibrometer collected data in the format used for the collection software (VibSoft), along with the raw ASCII and WAV conversions, and the time domain and spectrogram images for each.

** Please contact Payton Walker (prw0007@tamu.edu) if you have any questions.