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Posted by on Dec 23, 2014 | 5 comments

Time And Psychoacoustics

When designing audio we are often thinking of time across a large variety of units: samples, milliseconds, frames, minutes, hours and more. This article is inspired by a conversation I had with Andy Farnell about a year ago at a pub in Edinburgh, right before a sound design symposium, where we discussed about time and the role it plays when it comes to designing audio.

Like most other audio designers out there, I started twiddling the knobs and sliders well before I had an understanding of the underlying DSP. It was eye-opening experience to realise that almost every single DSP effect is related to time. So let’s start looking at a few common DSP tools used in everyday sound design and analyse how time and the precedence effect plays a role, starting from hundreds of milliseconds all the way down to a single sample.

Precedence Effect

The precedence effect is a psychoacoustic effect that sheds light on how we localise and perceive sounds. It has helped us understand how binaural audio works, how we localise sounds in space and also understand reverberation and early reflections. From Wikipedia:

The precedence effect or law of the first wavefront is a binaural psychoacoustic effect. When a sound is followed by another sound separated by a sufficiently short time delay (below the listener’s echo threshold), listeners perceive a single fused auditory image; its  spatial location is dominated by the location of the first-arriving sound (the first wave front). The lagging sound also affects the perceived location. However, its effect is suppressed by the first-arriving sound.

You might be familiar with this effect if you’ve done any sort of music production or mixing. Quite often a sound is hard panned to one of the two stereo speakers and a delayed copy (10-30ms) of the sound is hard panned to the other speaker. Our ears and brain don’t perceive two distinct sounds, but rather an ambient/wide-stereo sound. It is a cool technique for creating a pseudo-stereo effect from a mono audio source.

The first 30 seconds in the video below shows an example of the precedence effect in action. The delayed signal smears the original signal with phasing artefacts after which it seems to split from the original signal and become a distinct sound of its own.

Echos And Reverb

Echos are distinct delays. Reverberation is made up of early reflections which are delayed sounds that arrive first at the listener  (right after the direct sound) followed by a tail that consists of many such delays diffused into a dense cluster. Artificial reverbs are quite often approximated using networks of delays that feedback into each other (convolution reverbs behave a differently).

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Posted by on Dec 15, 2014 | 0 comments

“Hearing Lips and Seeing Voices” – The McGurk Effect

Want to see something that’ll mess with your head?

YouTube Preview Image

Now, you may not have noticed anything all that strange watching the video, but mute the sound and watch it again. After that, close your eyes and listen to just the audio. Notice anything strange now? You’ve just witnessed one of the more interesting perceptual illusions, the McGurk effect.

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Posted by on Dec 7, 2014 | 6 comments

Designing Sound Discussion Group – Psychoacoustics for Sound Designers

You can watch today’s webinar here on Designing Sound, or…if you’d like to ask questions…you can join us over on Google Hangouts to participate more directly. If you’d like to ask some follow up questions, please reach out to us through our contact page, ping me on twitter or drop a comment below.

Additional media used during the presentation after the break.

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Posted by on Dec 1, 2014 | 1 comment

It’s All in Your Head…

Image from Flickr user Allan Ajifo, used under a Creative Commons license. Click image to view source.

Image from Flickr user Allan Ajifo, used under a Creative Commons license. Click image to view source.

Have you ever stopped to consider the fact that all of the sounds we hear in our life are actually the result of post-processing in our brains? That what you hear might not actually be what the person next to you hears? The combination and coordination of organs that goes into the interpretation of fluctuations in atmospheric pressure is truly a marvel. We’ve given ourselves a pretty hefty challenge this month; we’re going to be focusing on Psychoacoustics. It’s not an easy subject to approach from a sound designer’s perspective, but we’re going to attempt it anyways.

…and rather than put together a separate announcement post…

This coming Sunday (December 7th), at 3:30PM U.S. Eastern, I’ll be hosting a webinar version of my AES “Psychoacoustics for Sound Designers” presentation. So, mark it on your calendars, and come to the site to watch…or go directly to our Google+ page so you can interact and ask questions during the presentation.

Next month’s featured topic will be Education. As always, we encourage contributions from the community. If you would like to contribute to this or next month’s discussions, or have something off-topic that you would like to share with the community, contact shaun {at} this website.

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Posted by on Jul 19, 2013 | 0 comments

New Research Initiative Will Dig Deep Into All Things Reverb

A project funded by the EU is taking on the challenge of modelling, synthesizing and analysing acoustic reverberation. The DREAMS (Dereverberation, Reverberation of Audio, Music and Speech) project began in February 2013 and is expected to run for three years. The research initiative is being led by the Katholieke Universiteit Leuven (Belgium), and will focus on four areas seen as pivotal to our understanding and experience of (de-)reverberation: room acoustics; signal processing; psychoacoustics; speech and audio processing. And although the research itself  is pretty technical it is expected that the findings could lead to improvements in a whole range of audio outputs and devices, such as tablets, mobile phones, etc. But will it fix the perennial problem of PA announcements at train stations?
Project website: http://www.dreams-itn.eu/

 

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