Espelhos Sonoros

Espelhos Sonoros (Sound Mirrors) is an art research project in sound mapping and streaming: a mobile stereo audio probe that provides a deep immersion in the city’s sound landscapes. 

The initial concept was made by Rodrigo Ramos, while I followed with the feasibility analysis, initial requirements for hardware and software.  This project was awarded by the Edital Elisabete Anderle de Estímulo à Cultura premium from Fundação Catarinense de Cultura.


As described in the project homepage:

O projeto Espelhos Sonoros consiste em uma releitura artístico-tecnológica de localizadores sonoros acústicos utilizados durante a Primeira Guerra Mundial (1914 – 1919) até 1940, quando se desenvolveu a tecnologia do radar, tornando-os obsoletos para fins bélicos. Tais objetos se assemelhavam a “conchas acústicas” e eram utilizados para localizar o movimento de aviões, navios e tanques no território de guerra.

Um exemplo de localizador acústico que inspirou o projeto

In a rough transcription:

The Sound Mirror project consists in a artistic-technical review of the acoustical locators used during the First World War (1914-1919) until the radar discovery in 1940, becoming obsolete for military purposes. Those objects resembled like acoustical shells and were used to locate and track the movement of planes, ships, and war tanks in the war field.

As an artist and sound designer, Rodrigo main interests revolves into sound mapping. So he wanted a device that could record and log location, and the possibilities of remote interaction and video recording. We came into terms of the following features:

  • Stereo/binaural audio and HD video capture and live streaming;
  • Mobile and itinerant artwork: the Sound Mirror should be light and autonomous enough to be carried around the city for live streamings;
  • Remote interaction: The streaming viewers can interact with the Sound Mirror by remotely controlling it’s motors;
  • GPS localization and log for sound mapping;


  • A single board computer with a lightweight OS;
  • Binaural microphones and a sound card with 2 mic level capture channels;
  • webcam or other camera module with easy specifications;
  • 4G and wifi support;
  • Lightweight and battery operated system;


The design was divided into the following parts:

  1. Electronic Hardware;
  2. Linux setup for networking, capture & streaming, peripheral interfaces;
  3. Web services, project website and user interaction;
  4. Visual concept and structure;
  5. Mechanical coupling between motor and structure;

Electronic Hardware

espelhos_sonorosxml (1)

hardware block diagram

  • Raspberry pi 2 B;
  • Binaural microphones;
  • raspicam camera module
  • wifi dongle;
  • 4G USB modem;
  • External USB soundcard;
  • Stepper motor + A4988 driver;
  • GPS module from microstack [tutorial];
  • high bright LEDs (10W);
  • Lithium power bank (20 Ah)
  • Li-poly 4S battery;
  • 12V buck regulator;
  • 20 x 4 saintsmart I2C display;

< insert schematics and pcb layout>

Linux (raspbian) configuration

  • raspi-config
  • alsa configuration
  • ffmpeg custom compilation for streaming
  • network config for a 4G modem connection
  • WiFi Access point for field setup and control
  • gpsd
  • Python modules for LCD I2C interface and motor control

All code and design files available at the project github [3]

Visual concept and structural design

The first sketches and models were make by João Eduardo Rabitto, Industrial Designer, and later improved by Advocir Oliveira.


First design sketches with the initial concept


Construction and assembly




Testing and results





  • Rodrigo Ramos – Concept and lead
  • Antonio Carlos Luppi – Electronic Design and prototyping, embedded linux
  • Mateus Dubiela Oliveira – Web application, back-end, and embedded linux
  • João Eduardo Rabitto – primary physical design;
  • Rafael Engels – mechanical power transmission design;
  • Advocir Oliveira – Adaptation and construction of the physical structure.

 Blog posts



External Resources

[1] Project homepage

[2] Sound mapping

[3] Project Github