The term acoustic originates from the Greek language and roughly translates as "able to be heard, audible"; this larger context further goes on to include the the physics of Noise and Sound related topics and their applications.

 

The fundamental classification of Noise and Sound comes from the understanding of how the user appreciates it, meaning that perception plays the key role in deciding what is noise and what is sound.

 

Sound, by far is the phrase that comes into use in audio engineering and that by itself is a sizeable segment of industry covering both the consumer and the manufacturer. From microphones to amplifiers, high fidelity speakers to recording studios, creating great acoustic environment to using state of the art electronics, a whole lot of products and processes are involved in both generating good sound quality and its reproduction.

 

The end delivery of a good quality sound is through the connected speakers; all the effort of creating a great sound is culminated in how the speakers reproduce them in a reasonably qualified listening space.

 

Speakers, over the years have evolved substantially, both in terms of the materials used in building them and the technology content. The magnets, voice coils, diaphragm cone material have all gone through paradigm changes to accomplish optimization in the size and performance. Obviously, this has also resulted in considerable price reduction.

 

Technically, speakers can be seen as an electro-dynamic shaker having magnets, drive coils and a termination platform that vibrates. However, the construction detailing and finesse is a subject of its own, governed by the application specifics.

 

Standard speaker configuration
 

Magnets are the key component of a speaker system; the magnetic strength (high gauss), high permeability and longevity to retain magnetic power over the usage life of the speaker, all play to accomplish this. The traditional ferrite magnets have been replaced by much efficient neodymium and alnico compositions helping the efficiency and overall quality of speakers.

 

The cone part of the speaker, also called the diaphragm, is the real reproducer of the electrical sound related signals into audible physical response. Many properties of the cone directly influence the quality of the sound being produced. Paper and pulp based materials are the default choice to make the diaphragms as they possess and retain excellent tuned properties over long period of usage.

 

Advances in polymers and composites have found their way into speaker diaphragms as well. Glass and carbon fibre, some forms of aramids (e.g., Kevlar) are all increasingly being used in advanced speaker designs to achieve better sound reproduction and extended performance life.

 

 
What's inside an over-the-ear headphone
 

One of the critical part of the speaker assembly is the suspension ring that forms the interface between the moving part of the speaker to the rigid static frame used for mounting the speaker unit onto a box. The sustained physical linearity, homogeneity and elastic recovery constants of the suspension material decides the response and the operating frequency range of the speaker.

 

There are many jargons and technically non-complying terminologies associated with speakers and sound reproduction systems. The definition of acoustic wattage and frequency response of the speakers are much overstated, not taking into consideration how these are derived and what it makes sense to the user. While most of these specifications needs to be read and understood in conjunction with the amplifiers and electronics involved in processing the sound content, its much often used as a commercial selling proposition than any value addition.

 

Detailing of In-ear headphone
 

The combined progress in electronics, digital signal processing, sound reproduction and its synthesis have made notable improvements in the listening quality and user experience. These advances have percolated into speakers systems of miniature size that are in used in head phones, hearing aids and other specialized applications.

 

NV Dynamics works with many of high end speaker and sound reproduction companies assisting them in their testing and validation processes. How the "sound should sound right" is something that we are both learning and delivering as a part of this journey of Noise and Vibration Engineering.