Audiometric Data

Professional equipment with linear frequency response was used to carry out the technical measurements of “Volume”.

Reference tools used

The tools used for audiometric measurements.

The following reference signals were used for the test:
• PinkNoise
• Sweepsine20Hz-20kHz • 200Hz
• 350Hz
• 1kHz
• 10kHz
• A Daft Punk song

The smartphones that can be used within “Volume” are all phones that have speakers on the lower base. Specifically for the test the following were used:
• Smartphone One Plus 6T
• DPA4090 condenser omnidirectional microphone
• Focusrite Red7 microphone preamplifier
• ADOrion32 + Gen3 converter
• Measuring tools Waves and Fab Filtertaratic as follows: -12dB = 0VU

How it sounds?

The simple device is able to increase the volume of the smartphone sound by about 8dB as shown in fig 1 and 2.

In the first figure you can read a frequency of 1kHz reproduced and measured directly by the smartphone.
In the second figure, the same source through “Volume” .

The frequency response is the typical one of horn loads and therefore, compared to the measurement carried out directly on the smartphone, we can read from the figures a slight lack of bandwidth extremes reproduced by the smartphone in the field free.

Sound Spectrum

Analysis of sound linearity

The smartphone’s sound spectrum measurement while playing a piece of music has a linear frequency response from 260Hz to 20kHz. (fig. 3)
The same track played inside “Volume” has a frequency response ranging from 340Hz to 19kHz. (fig. 4)

The linearity of the sound, in addition to the extremes of the band slightly limited by the effect of the horn loading, is compromised by a sudden loss of signal at the frequency of 3.8kHz, due to the effect of phase cancellations that occur inside the cone . This frequency is extremely limited when playing a Pink Noise and in any case does not affect when listening to a piece of music.

This frequency could change and be shifted up or down by changing the diameter of the cone neck.

Being a passive amplifier “Volume” it is not able to extend the frequency spectrum of the smartphone up or down, but by analyzing single sinusoids reproduced through the cone, it is can verify that the device does not alter its height within the sound spectrum.

However, it is interesting to be able to clearly read from these measurements an emphasis of the even higher 3rd harmonic of the same frequencies, which will result in a richer sound in terms of harmonics.

1kHz sinusoid in free field and through “Volume”