Title in audio

ASTER Demonstration

AsTeR is dedicated to my Guide-Dog. AsTeR --Audio System For Technical Readings-- is a computing system for rendering technical documents in audio. AsTeR was developed by T. V. Raman for his PhD. (141 pages) An audio formatted version of the thesis, (approximately 6 hours) produced by AsTeR, is being made available by RFB (Recordings For the Blind as the first computer generated talking book. Here is the abstract in print, and here is an audio formatted version.

This hypertext document demonstrates the audio renderings generated by AsTeR. Each example is made up of three components:

  1. The original LaTeX input.
  2. The audio formatted output produced by AsTeR. The speech is produced by a Dectalk, and has been digitized at 8-bit mulaw AsTeR uses stereo to render tables, an effect that is not conveyed by the 8-bit mono encoding.
  3. The visually formatted version produced by LaTeX and DVIPS.

Section 1 simple fractions and expressions.

This set of 8 examples demonstrates the use of voice inflection and pauses to convey grouping of sub-expressions succinctly.

The state of the audio formatter is a point in audio space. Here, audio state was varied along a dimension in audio space before rendering sub-expressions. This is equivalent to parenthesizing in the visual context.

Section 2 superscripts and subscripts.

To convey subscripts, superscripts, and other visual attributes, AsTeR varies audio state along a dimension that is orthogonal to (independent of ) the dimension used to convey sub-expressions. This allows the nesting of these mutually independent concepts. The following 6 examples demonstrate how superscripts and subscripts are rendered unambiguously.

Section 3 Knuth's examples of fractions and exponents.

These examples are taken verbatim from the TeX Book, by Donald Knuth. They are used in the TeX Book to demonstrate the power of the TeX layout operators. Notice that all of these examples comprise of the same 6 symbols, but are very different! AsTeR renders these 7examples as unambiguously as TeX.

Section 4 A continued fraction.

Moving along a dimension in audio space defines a perceptibly monotonic change. This notion of perceptible monotonicity is vital in conveying nesting.

Math Audio LaTeX Postscript

Section 5 Simple School algebra.

Here are 3 examples from school algebra.

Section 6 square roots.

Notice the choice of unambiguous renderings for the following 3 expressions:

Section 7 Trigonometric identities.

Written mathematical notation can be ambiguous and hard to recognize. Notice the complete absence of parenthesis in some of the examples below. AsTeR uses several heuristics to construct the correct tree structure for these 7 expressions.

Section 8 Logarithms.

Notice the context-specific rendering of these 4 expressions when speaking the base of the logarithm. The renderings are chosen to reduce cognitive load;
log base a of x
as opposed to
log of x to the base a

Section 9 Series.

Context-specific rendering rules allow AsTeR to interpret the superscripts in these 5 examples as exponents. Such interpretation is not hard-wired into the renderings; it is fully customizable by the user.

Section 10 Integrals.

The first of these 6 integrals, probably the most innocuous, is also the most difficult to recognize; it is impossible to determine the variable of integration.

Section 11 Summations.

Here are 3 summations. Notice that the same expression can be written in more than one way.

Section 12 Limits.

Here are 2 limits

Section 13 Cross referenced equations.

The following example is meant to illustrate AsTeR's rendering of cross-references, and is most effective when AsTeR is used interactively.

AsTeR enables the listener to give meaningful names to cross-referenceable objects, and uses these names when referring to such objects in later cross-references.

Section 14 Distance formula.

Notice that AsTeR produces good intonational structure when speaking text that is intermixed with mathematics. Math Audio LaTeX Postscript

Section 15 Quantified expression.

The quantifiers present an interesting challenge to AsTeR's recognizer. Math Audio LaTeX Postscript

Section 16 Exponentiation.

Once again, perceptible monotonicity allows AsTeR to convey the following 3 examples deeply nested expressions succinctly.

These examples were produced with the Emacs Calculator, a full-fledged symbolic algebra system. AsTeR interfaces directly with this calculator, and renders the output just as well as any document.

Section 17 A generic matrix.

AsTeR uses stereo effects to convey the two-dimensional structure of the matrix. Rendering commences on the left, and moves progressively right as each element of any row is spoken.

Math Audio LaTeX Postscript

Section 18 Faa de Bruno's formula.

This section presents Faa De Bruno's formula, taken from Knuth's Art Of Computer Programming, Vol. 1. I first heard it spoken by a RFB reader on a talking book; it took 120 seconds to speak.

Since the renderings produced by AsTeR utilize features of the audio space not available to a human reader (I still have not met a reader who can change the size and shape of her head as she talks:-) the rendering takes under 80 seconds.

As you will hear soon, even this is too long; you forget the beginning by the time you hear the end.

Later, we present rendering using variable substitution, a powerful technique for conveying top-level structure of complex expressions.

AsTeR can process complex expressions like the above, and upon request, replace complex sub-expressions with meaningful identifiers. Such renderings convey top-level structure; the listener can then listen to the sub-expressions separately.

Since this substitution process is performed by AsTeR, there is no LaTeX or Postscript equivalent for the audio output in this case.

T.V. Raman raman@crl.dec.com
Last modified: Wed Aug 10 19:56:56 1994