A sound and signal processing glossary

Bit / Byte: These are the units that we use to measure information. A single bit of information can hold one of two values (i.e. 0 or 1). The more bits we have, the more ‘potential’ values we can represent, therefore the more information we have. For example, 4 bits gives us 16 possible different values, which is 4 times more information than a single bit. A single byte is 8 bits, and a kilobyte is  1024 bytes.

Data rate: This tells us how fast information (i.e. data) can be transferred. It’s typically measured in bits (b), bytes (B), or kilobytes (KB) per second.  

Decibel (dB): The decibel is simply a unit of measurement for a logarithmic ratio. In acoustics, the decibel is the unit of measurement for Sound Pressure Level and is referenced against 20μPa - the threshold of human hearing at 1kHz.

Device Agnosticism: The capability of a piece of technology to be applied to a wide array of use cases or applications without special modification, adaptation or extraneous infrastructure.

DSP (Digital Signal Processing) : The use of digital tools such as general purpose computers or specialised processors to analyse, modify, optimise or otherwise process a signal being represented as a series of discrete values in time.

Frequency: The rate at which something happens within a period of time - usually per second. For audio, this means the rate at which air particles are vibrating back and forth - which is what we (usually) perceive as the fundamental 'pitch' of a note. Frequency is measured in 'Hz' which is the number of oscillations per second.

Hertz (Hz): Unit of measurement for periodic systems where 1Hz is equal to one cycle or one whole period per second.

Loudness: 'Loudness' is an umbrella term which describes our perception of Sound Pressure Level (SPL). Several factors combine to produce a sense of how loud a sound is including its SPL, its frequency content and how distorted it is amongst other factors.  

Payload: This is the actual information that we want to be sent. When we transmit data, there is often some additional information added to the signal to help with the transmission, that is not part of the payload. You can think of it like receiving a package from a large well known large online retailer. You might order a pair of socks (e.g. the payload), but what you receive is a box with loads of packaging and padding. The extra stuff is just there to make sure the payload (your socks) arrive in one piece (or two!).

Protocol: This is the set of parameters that we fine tune to meet specific range, reliability, and data rate requirements for our customers. We offer standard protocols that provide a nice balance of good range, data rate, and reliability. This works great for many use cases, but sometimes one factor is more or less important than the others. This is where we can work with customers to develop custom protocols specific to individual use-cases.

Reliability: When we send data over the air (or even down cables), it is not always received properly at the other end. One of the major challenges in data-over-audio is ensuring information successfully travels through the air without being lost in noise, or distorted by reverb. Reliability can be measured in many ways, however for our purposes we will consider it as the percentage of times a sent payload is successfully received at the other end.

Range: The distance that information can be sent. With data over-sound, this is partly determined by how loud the speaker is, but there are also other important factors that feed into the possible range, such as the reliability and required data rate.

Sound Pressure Level: Measured in decibels (dB) Sound Pressure Level (SPL) is the local pressure change caused by a sound wave as it moves through the air. We - roughly speaking - perceive this as loudness or volume.

Ultrasound: Audio frequencies which are above the range of human hearing. This is academically defined as above 20kHz, though most of us have an upper threshold for hearing that is substantially lower that this, and is most often a function of a person's age.