Expochirp used to check ReS (Resonant String Shell) - Measurements results B-Format

Once I have evaluated the acoustic parameters for SPL and C80 in each point, I decided to check the spatial coefficients to check if the structure was performing any good in increasing the Apparent Source Width (LFE4) and the spaciousness (BQI, Binaural Quality Index).

To evaluate the latter from a B-Format Impulse Response, I needed to convert this in binaural by using an ambisonic in-phase decoder and HRTF data from the CIPIC library (http://interface.cipic.ucdavis.edu/sound/hrtf.html).

This is not the optimal conversion technique (as demonstrated in this paper http://infoscience.epfl.ch/record/138612/files/2011_Menzer_IEEE%20Trans%20on%20Audio_05456170.pdf?version=2) but it was the one currently easily available to me; it shows errors in the interaural coherence compared to measurements, hence in the evaluation of the coming direction of sound.

From the results we can see that:

  1. There is not a linear reduction of the lateral efficiency when we go further away from the structure but there is an increase in the last point, most probably due to the side building.
  2. All LFE4 values stays in the optimal range
  3. BQI is above the optimal range and is all in the order of 0.9 or more, this is due to the increase of early reflections to the receivers and the absence of reverberant tail that provides more cross correlation between the ears.
  4. The side building plays an important role in the diversity between left and right ear response.

As an overall analysis, I am quite happy so far for the results achieved.

I have to take into account that this is not a concert hall, where there is a room that provides early an late reflections, and that the optimal ranges mostly do not apply to this project.

It is very difficult to find results for these kind of structures in the literature due to the lack of similar projects.

I am studying more about further improvements and will be posted soon more results, hopefully!!!

Expochirp used to check ReS (Resonant String Shell) - Measurements results

As discussed in the previous post, I am presenting the results of the Impulse response measurements made to check the acoustic quality of ReS.

The measurements have been performed with a omnidirectional source placed under the acoustic shell in central position and on the sides in the same position as the violins and the cellos in chamber music sextet configuration.

Receiver positions are in the middle line in front of the shell respectively at the following distances from the external front line of the shell:

  1. R01 - 0.5m
  2. R02 - 1m
  3. R03 - 2m
  4. R04 - 4m
  5. R05 - 8m
  6. R06 - 16m

Measurements shows the following objective acoustic parameters (ISO 3382):

  1. SPL
  2. C80
  3. LFE4
  4. BQI (1-IACCE)

The following papers discuss the ideal values for the parameters in use.

http://www.akutek.info/concert_hall_acoustics_files/parameters.htm

http://www.leoberanek.com/pages/eightyeighthalls.pdf

First of all, I have measured the IR without the structure in place to evaluate the benefits of including it in the courtyard.

No Shell

Measurements only in R01

It can be easily seen the lack of low frequency in the receiver points from the sound source and the already high value of C80 (typical of semi-opened space).

ReS 2012

The first year of the festival with ReS in place, has shown already good results (far from the optimal but a good start) in the SPL evaluation at every receiver point and an increase in the C80 parameter.

It can be spot that there is a slight increase in the frequency response of the signal at the receptor (especially at 125 Hz and at mid-frequency) and an improvement in the C80 values.

The improvement in the acoustic response is far from optimal and a very slight increase compared to the case without the shell installed.

The reason has been found in the large opening between the panels and in the vibrating panels as they were all suspended using strings.

ReS 2013

The last version of ReS has corrected most of the mistakes of the first version, increasing the signal frequency response and the Clarity at any receptors, especially at low frequencies.

From the results above we understand that there is a difference of the response when we move the source in violins or cellos position and that the  R05 sin (Left) an R05 dx (right) positions have not a uniform response.

In my view this is due to the side building reflections and to the asymmetry of the audience area.

Measurements shows anyway a very promising increase in the low frequency response of the signal at each receivers’ position and in the C80 values at the same low frequency range.

It can be seen that C80 values are above the typical range for concert halls but I expect this result as in our case we do not have an enclosed space but just a structure improving the early reflections amount at the receiver points.

Expochirp used to check acoustic performance of ReS (Resonant String Shell)

As anticipated in previous posts, Expochirp has been used to measure the acoustic performance of ReS during villapennisinmusica festival (http://villapennisinmusica.wordpress.com/) in 2012 and 2013.

The design of the structure is part of a research project in collaboration with CMMKM Architects (http://www.cmmkm.com/) where my role is to look after the acoustic design.

I have used Expochirp to measure Impulse Responses (omnidirectional mic and A-Format Mic) in order to evaluate ISO3382 parameters and judge the acoustic quality.

As you can see from the picture below, the structure is in a courtyard on the backside of one of the major building in the town of Acireale (Sicily, Italy), with the building itself being on the right side of the audience and the shell on one end of the courtyard.

Over the 2 years the research project has been conducted, the acoustic hell has changed shapes many times, in order to optimize the acoustic response for  the audience and the musicians, reaching the two final forms shown below.

ReS 2012

ReS 2013

In the next post there will be more detailed results.

Villa Pennisi in Musica 2013, ReS and ExpoChirp

ExpoChirp has been used extensively to test the excellent ReS2.0 (Resonant String Shell) in Villa Pennisi during the Villa pennisi in Musica festival 2013.

The festival is the perfect occasion to develop cutting-edge design for an acoustic shell used for chamber music concerts outside and to develop the research in analysis of 3D Impulse Responses using a B-Format mic.

The results will be posted soon but please check the festival website for more info: http://villapennisinmusica.wordpress.com/

For those interested the festival hosts also a classical music masterclass and an Architectural acoustics workshop; edition 2014 will be announced soon.

ReS2.0 during the inauguration concert of Villapennisinmusica festival (Foto by Sonia Ponzo)

Ambisonics reproduction for live popular music acts

Just back from the excellent Reproduced Sound Conference organized by the Institute Of Acoustics in Manchester (UK).

It has been a very interesting and acoustics intensive 3-days marathon where there have been a lot of interesting papers together with the right amount of time to do a lot of networking with acousticians, software designers, sound engineers and young and less young colleagues.

As posted previously, I have been presented my project for the application of ambisonics reproduction techniques for popular music.

The presentation has been well received and, although the last paper of the conference, many people attended.

I am very happy about the feedback and really grateful to many who have taken the time to chat with me after the presentation.

Below you can find two links to know more about the project:

Paper: https://db.tt/OdcUB0Ji

Presentation: https://db.tt/ZufxykLU

I would be really grateful if you would like to share your thoughts on the project and happy to receive messages if would like to discuss further.

and above all, ENJOY!!

Paper on ambisonics reproduction for live popular music acts

Another great news!!

I will be presenting a paper at the Reproduced Sound 2013 conference in Manchester (http://www.reproducedsound.co.uk/index.php/programme).

It will be the last paper presented in the conference program and I hope it will be interesting and entertaining!!

Abstract:

USE OF AMBISONICS REPRODUCTION TECHNIQUES FOR POPULAR MUSIC – A JAZZ MUSIC CONCERT APPLICATION

S Di Rosario, Buro Happold Engineers LtD

Ambisonics has been used in many experimental and electroacoustic music applications, being able to deliver a mesmerizing soundscape to the audience. Applications to popular music have been quite rare and very difficult to achieve for the musicians and for the engineer/audio artist. This paper presents a case study of a practical application of Ambisonics reproduction techniques to popular music, in the particular case of a jazz concert. The author has been invited to create bespoke software that could have been flexible and operable in real time, allowing the “Ambisonics Sound Engineer” to be part of the band on stage as an additional musician. 

I will be presenting as an employee of Buro Happold Ltd (my current job) a work I have done separately by the typical core work we do in the Acoustics team.

The application and all the research behind it, helped me to improve our current ambisonics system used mainly for audio demonstrations (Auralisations) of our work to the clients.

It is very interesting how a musical application can help understand and improve a more scientific application for demonstrating acoustic design to person that are acoustics-literate.

Expochirp has been used in this application to measure first-order B-Format IR of spaces and applied to the ambisonic reverb.

I will post the link to the full paper after the conference.

Teaching in Colombia

I am very proud to announce that I will be teaching three courses at the Universidad de San Buenaventura in Medellin, Colombia.

http://www.usbmed.edu.co/Programas_academicos/Ingenierias/web/pregrado/Ingenieria_de_Sonido.aspx

The topics are (in Spanish):

  • Diseño de una concha acústica por música acustica en vivo
  • Diseño y practicas por un sistema de reproducción de audio 3D (Ambisonics) por actos de música popular
  • Técnica de medidas de características acústicas de recintos

The courses dates are still not fixed but I will be in Colombia for about 4 months (between February 2014 and July 2014) and the teaching will happen in these times.

If you happen to be in Medellin and you are interested in the topics, you are welcome to write to me for more technical information about the courses; I will post all my research on the topics above in this blog.

Please contact the Universidad de San Buenaventura for more info.

Expochirp blog restarting

We have been very busy in the 1 year and we have been unfortunately forced to stop posting developments on this blog.

But now we are back!!!

The idea is to use this blog to post all the research topic we are investigating at the moment which include not only expochirp but also research in Architectural acoustics for chamber music and in Ambisonics surround sound reproduction.

More details to follow!!

ExpoChirp for improving your sound during gigs!!! Really???

What about if you can use an open source software to do quick measurements during gigs and improving the reproduced sound quality of that scrappy club you used to play in?

This is one of our next challenges: to develop a module for ExpoChirp for PA system calibration and room correction.

Katja is doing an amazing study on long FIR filter with low latency.