All you need to know about Impulso
High Accuracy Acoustic App Engineered by Artnovion
Impulso is an app for measuring room acoustics. It allows you to measure the acoustic response of your room using your iPhone. You can view the reverberation time (RT) in octave bands and then simulate how the acoustic response of your room is improved when adding Artnovion acoustic products. You can also check the frequency response of your measurement. It is compatible with built-in or external microphones.
For optimal measurements we recommend the use of an external full range speaker and a measurement grade microphone connected to the headphone/microphone socket of the iPhone (Bluetooth and WiFi connections are being developed for a future update). Please follow the diagram below for instructions on connecting your hardware.
Please note that if you are connecting to an external speaker, but not an external microphone, the internal microphone will be used for the measurement, provided you have the appropriate cable without a microphone connection.
What do I need to know when using Impulso?
Impulso uses the sine-sweep method to ping the room. The frequency range is 20Hz to 20KHz and the length is 10 seconds. This should be sufficient to measure in most conditions. However you should note a few issues:
1) If you are measuring spaces with an expected reverberation of well beyond 10 seconds, artefacts may appear in the capture signal that cannot be accounted for. In these cases it is possible that you will get erroneous results.
2) Reverberation is an acoustic response that is based on a number of assumptions about the sound field. One of these is the fact that the reverberant sound field doesn't change between positions in the same room. Whilst this is the theoretical basis for the concept, in reality these conditions are typically not met, particularly in smaller, less reverberant rooms. For this reason, the international standard for reverberation time measurements recommends that a number of positions are averaged in order to define the RT of a given room. Impulso does not carry out this average and should be used mainly to get an indication of the response at a given position within the room for a set loudspeaker position. We recommend you carry out the measurement using one of the loudspeakers in your monitoring or home cinema system and place the microphone (or iPhone) in the listening position. This way you obtain the response of your room in its current setup
Why doesn't my measurement appear? The App keeps asking to repeat the measurement.
Firstly, make sure you can clearly hear the measurement signal produced by the iPhone speaker (or external speaker if connected).
There is a validation process running in the app that prevents it from displaying results when the measurement is invalid. This may happen because the measurement signal is not being picked up properly and/or the signal to noise ratio of your measurement is not sufficient to compute reverberation times. To solve this, try increasing the volume of the test signal in the measurement screen and reduce the background noise in the environment. However, if the test signal is too loud, it may distort the microphone input, and needs to be lowered accordingly.
I get unusual values in some octave bands
If during the measurement the microphone captures external noises, particularly impulse noise, the calculation of the RT values may be inaccurate. Try to reduce the background noise in your room and repeat the measurement. Also, avoid placing the microphone too close to surfaces such as walls, floor or tables.
Should I trust the measurements if I am using the iPhone speaker?
I get strange values at very low and very high frequencies
The loudspeaker built into the iPhone has a restricted frequency range, that is, it cannot produce very low and very high frequencies. For this reason, your measurement cannot be reliable at very low and very high frequency values. If measuring with the built in speaker we recommend you disregard any values below 1000 Hz.
The RT values change between measurements
An acoustic sound field is not stationary. It is influenced by temperature and humidity changes, plus any movement within the room, such as people moving around, coming in or out. Also, even though you think you have not moved the microphone or speaker, a very slight change will expose these to different reflection patterns. Additionally, having doors open or closed will affect measurements. We recommend that you always measure in a quiet space, with all doors and windows closed and avoid moving about when taking the measurements. If you want to repeat measurements we suggest you use an external speaker and microphone and mount these on stands to prevent movement between measurements.