Homomorphic signal processing techniques are used to place information imperceivably into audio data streams by the introduction of synthetic resonances in the form of closely spaced echoes These echoes can be used to place digital identi cation tags directly into an audio signal with minimal objectionable degradation of the original signal

In two-dimensional echocardiographic studies of left ventricular thrombus in patients, an unusual pattern of dynamic left ventricular intracavitary echoes was identified in some hearts with severe apical dysfunction. These intracavitary echoes were noted in the apical region and were distinct from left ventricular thrombi. Certain features of the intracavitary echoes suggested that they were ge...

IN previous communications (Oksala and Lehtinen, 1959; Oksala 1960a, b), I noted that vitreous haemorrhages reflected echoes on the screen of an ultrasound equipment, and that these echoes were clearer if a fresh haemorrhage was involved. I also found that old haemorrhages, on account of the destruction of the vitreous, do not always become visible in ultrasonic examinations (Oksala and Lehtine...

In two-dimensional echocardiographic studies of left ventricular thrombus in patients, an unusual pattern of dynamic left ventricular intracavitary echoes was identified in some hearts with severe apical dysfunction. These intracavitary echoes were noted in the apical region and were distinct from left ventricular thrombi. Certain features of the intracavitary echoes suggested that they were ge...

A central theme of this thesis is using echoes to achieve useful, interesting, and sometimes surprising results. One should have no doubts about the echoes’ constructive potential; it is demonstrated masterfully by Nature. Just think about the bat’s intriguing ability to navigate in unknown spaces and hunt for insects by listening to echoes of its calls, or about similar (albeit less well-known...