Skip to content Skip to navigation

Connexions

You are here: Home » Content » Formant (Vowel) Synthesis

Navigation

Content Actions
  • Download module PDF
  • Add to ...
    Add the module to:
    • My Favorites
    • A lens
    • An external social bookmarking service
    • My Favorites (What is 'My Favorites'?)
      'My Favorites' is a special kind of lens which you can use to bookmark modules and collections directly in Connexions. 'My Favorites' can only be seen by you, and collections saved in 'My Favorites' can remember the last module you were on. You need a Connexions account to use 'My Favorites'.
    • A lens (What is a lens?)

      Definition of a lens

      Lenses

      A lens is a custom view of Connexions content. You can think of it as a fancy kind of list that will let you see Connexions through the eyes of organizations and people you trust.

      What is in a lens?

      Lens makers point to Connexions materials (modules and collections), creating a guide that includes their own comments and descriptive tags about the content.

      Who can create a lens?

      Any individual Connexions member, a community, or a respected organization.

    • External bookmarks
  • E-mail the author

Lenses

What is a lens?

Definition of a lens

Lenses

A lens is a custom view of Connexions content. You can think of it as a fancy kind of list that will let you see Connexions through the eyes of organizations and people you trust.

What is in a lens?

Lens makers point to Connexions materials (modules and collections), creating a guide that includes their own comments and descriptive tags about the content.

Who can create a lens?

Any individual Connexions member, a community, or a respected organization.

This content is ...

In these lenses

  • NI Signal Processing

    This module is included inLens: Digital Signal Processing with NI LabVIEW and the National Instruments Platform
    By: Sam ShearmanAs a part of collection:"Musical Signal Processing with LabVIEW (All Modules)"

    Comments:

    "This online course covers signal processing concepts using music and audio to keep the subject relevant and interesting. Written by Prof. Ed Doering from the Rose-Hulman Institute of Technology, […]"

    Click the "NI Signal Processing" link to see all content selected in this lens.

Recently Viewed

Tags

(What is a tag?)

These tags come from the endorsement, affiliation, and other lenses that include this content.

Formant (Vowel) Synthesis

Module by: Ed Doering

Summary: Speech and singing contain a mixture of voiced and un-voiced sounds (sibilants like “s”). The spectrum of a voiced sound contains characteristic resonant peaks called formants caused by frequency shaping of the vocal tract. In this module, a formant synthesizer is developed and implemented in LabVIEW. The filter is implemented as a set of parallel two-pole resonators (bandpass filters) that filter a band-limited pulse source.

LabVIEWq.png This module refers to LabVIEW, a software development environment that features a graphical programming language. Please see the LabVIEW QuickStart Guide module for tutorials and documentation that will help you:
• Apply LabVIEW to Audio Signal Processing
• Get started with LabVIEW
• Obtain a fully-functional evaluation edition of LabVIEW

Introduction

Speech and singing contain a mixture of voiced and un-voiced sounds. Voiced sounds associate with the vowel portions of words, while unvoiced sounds are produced when uttering consonants like "s." The spectrum of a voiced sound contains characteristic resonant peaks called formants, and are the result of frequency shaping produced by the vocal tract (mouth as well as nasal passage), a complex time-varying resonant cavity.

In this module, a formant synthesizer is developed and implemented in LabVIEW. The subtractive synthesis model of a wideband excitation source shaped by a digital filter is applied here. The filter is implemented as a set of parallel two-pole resonators (bandpass filters) that filter a band-limited pulse. Refer to the modules Subtractive Synthesis Concepts and Band-Limited Pulse Generator for more details.

Formant Synthesis Technique

The Figure 1 screencast video develops the general approach to formant synthesis:

Figure 1: [video] Formant synthesis technique
Figure 1 (sub_formants-technique.html)

The mathematics of the band-limited pulse generator and its LabVIEW implementation are presented in the module Band-Limited Pulse Generator.

The two-pole resonator is an IIR (infinite impulse response) digital filter defined by Equation 1 (see Moore in the "References" section for additional details):

H(z)=(1−R) 1−R z −2 1−2Rcos⁡θ z −1 + R 2 z −2 H(z)=(1−R) 1−R z −2 1−2Rcos⁡θ z −1 + R 2 z −2 MathType@MTEF@5@5@+=feaagaart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLnhiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYb1uaebbnrfifHhDYfgasaacH8YjY=vipgYlh9vqqj=hEeeu0xXdbba9frFj0=OqFfea0dXdd9vqai=hGuQ8kuc9pgc9q8qqaq=dir=f0=yqaiVgFr0xfr=xfr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamisaiaacIcacaWG6bGaaiykaiabg2da9iaacIcacaaIXaGaeyOeI0IaamOuaiaacMcadaWcaaqaaiaaigdacqGHsislcaWGsbGaamOEamaaCaaaleqabaGaeyOeI0IaaGOmaaaaaOqaaiaaigdacqGHsislcaaIYaGaamOuaiGacogacaGGVbGaai4CaiabeI7aXjaadQhadaahaaWcbeqaaiabgkHiTiaaigdaaaGccqGHRaWkcaWGsbWaaWbaaSqabeaacaaIYaaaaOGaamOEamaaCaaaleqabaGaeyOeI0IaaGOmaaaaaaaaaa@52CF@ (1)

where θ=2π ( f C / f S ) θ=2π ( f C / f S ) MathType@MTEF@5@5@+=feaagaart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLnhiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYb1uaebbnrfifHhDYfgasaacH8YjY=vipgYlh9vqqj=hEeeu0xXdbba9frFj0=OqFfea0dXdd9vqai=hGuQ8kuc9pgc9q8qqaq=dir=f0=yqaiVgFr0xfr=xfr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeqiUdeNaeyypa0JaaGOmaiabec8aWnaalyaabaGaaiikaiaadAgadaWgaaWcbaGaam4qaaqabaaakeaacaWGMbWaaSbaaSqaaiaadofaaeqaaaaakiaacMcaaaa@3FC1@ , R= e −πB/ f S R= e −πB/ f S MathType@MTEF@5@5@+=feaagaart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLnhiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYb1uaebbnrfifHhDYfgasaacH8YjY=vipgYlh9vqqj=hEeeu0xXdbba9frFj0=OqFfea0dXdd9vqai=hGuQ8kuc9pgc9q8qqaq=dir=f0=yqaiVgFr0xfr=xfr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOuaiabg2da9iaadwgadaahaaWcbeqaaiabgkHiTiabec8aWjaadkeacaGGVaGaamOzamaaBaaameaacaWGtbaabeaaaaaaaa@3E43@ , f C f C MathType@MTEF@5@5@+=feaagaart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLnhiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYb1uaebbnrfifHhDYfgasaacH8YjY=vipgYlh9vqqj=hEeeu0xXdbba9frFj0=OqFfea0dXdd9vqai=hGuQ8kuc9pgc9q8qqaq=dir=f0=yqaiVgFr0xfr=xfr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOzamaaBaaaleaacaWGdbaabeaaaaa@371A@ is the center frequency, B B MathType@MTEF@5@5@+=feaagaart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLnhiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYb1uaebbnrfifHhDYfgasaacH8YjY=vipgYlh9vqqj=hEeeu0xXdbba9frFj0=OqFfea0dXdd9vqai=hGuQ8kuc9pgc9q8qqaq=dir=f0=yqaiVgFr0xfr=xfr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOqaaaa@3602@ is the bandwidth, and f S f S MathType@MTEF@5@5@+=feaagaart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLnhiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYb1uaebbnrfifHhDYfgasaacH8YjY=vipgYlh9vqqj=hEeeu0xXdbba9frFj0=OqFfea0dXdd9vqai=hGuQ8kuc9pgc9q8qqaq=dir=f0=yqaiVgFr0xfr=xfr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOzamaaBaaaleaacaWGdbaabeaaaaa@371A@ is the sampling frequency, all in units of Hz.

The Figure 2 screencast video shows how to create a subVI that implements the two-pole resonator.

Figure 2: [video] Implementing the two-pole resonator in LabVIEW
Figure 2 (sub_formants-twopole.html)

Formants for Selected Vowel Sounds

Peterson and Barney (see "References" section) have compiled a list of formant frequencies for common vowels in American English; refer to Figure 3:

Figure 3: Formant frequencies for common vowels in American English (from Peterson and Barney, 1952)
Figure 3 (sub_formants-voweltable.png)

Formant Synthesizer

The previous sections have laid out all of the pieces you need to create your own formant synthesizer. See if you can set up a LabVIEW VI that pulls the pieces together. The Figure 4 screencast video shows how your finished design might operate. The video also discusses how to choose the relative formant amplitudes and bandwidths, as well as the BLP source parameters.

Figure 4: [video] Formant synthesis LabVIEW VI
Figure 4 (sub_formants-formantsynth.html)

References

  • Moore, F.R., "Elements of Computer Music," Prentice-Hall, 1990, ISBN 0-13-252552-6.
  • Peterson, G.E., and H.L. Barney, "Control Methods Used in a Study of the Vowels," Journal of the Acoustical Society of America, vol. 24, 1952.

Comments, questions, feedback, criticisms?

Send feedback